Special thanks to Laurence BonJour and Ann Baker, authors of Philosophical Problems: An Annotated Anthology, for their contributions to this section.

Many of the concepts expressed by terms in this glossary are ones about which many philosophers have doubts or misgivings: as to their ultimate intelligibility, their application to the world, or both; we have not, for the most part, attempted to take note of such doubts and misgivings here.

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

abduction See explanatory argument.

abstract / concrete A metaphysical distinction between modes of being. Concrete things are things that exist in space and time and causally interact with other such entities, or things that exist in the same general way. Thus an ordinary material object is a paradigm of a concrete thing, but the mind or spirit of a particular individual person (according to dualism) resembles a material object in that it exists in time and on most views stands in causal relations the person's body (a material thing), and thereby also counts as concrete. God, though on some views existing outside of both space and time, is still concrete by virtue of his causal relation to the world. Abstract things or entities, in contrast, do not exist in space and time, and do not causally interact with concrete entities. The paradigm of an abstract entity would be an abstract property such as redness or triangularity or justice. But things like numbers and sets of objects are also standardly regarded as abstract in the same way.

act utilitarianism See utilitarianism.

ad hoc Responses or qualifications given merely for the purpose of meeting some objection or problem without having any independent merit (the Latin phrase literally means "for this specific purpose").

agnosticism See theism.

altruism See ethical egoism.

analogy, argument by Arguing from the similarity between things in one respect to the conclusion that they are thereby (probably) similar in another respect.

analytic / synthetic This is a distinction concerning the structure of a proposition, claim, or statement. The fact that a proposition is analytic is often offered (especially by proponents of moderate empiricism) as an explanation of how it can be justified or known a priori. As Kant defines the distinction, an analytic proposition is one of subject-predicate form whose predicate is included in its subject, either explicitly (all tall men are tall) or implicitly (all bachelors are unmarried); while a synthetic proposition is one that does not have this sort of form, one in which the predicate is not contained in the subject. Other accounts of analyticity have been offered in an attempt to account for the apparent a priori status of propositions that do not clearly fit Kant's definition. Of these, the two most common are (i) that a proposition is analytic if it is a truth of logic or transformable into a truth of logic by substituting correct definitions for some of its terms; and (ii) that a proposition is analytic if it is true just by virtue of its meaning (and, in both cases, otherwise synthetic). Here definition (i) is a fairly obvious generalization of Kant's definition, which would include the propositions that fit his definition, but also propositions like either it is raining or not raining. Definition (ii), on the other hand, is more vague: just how does meaning account for truth?. (If it means only that anyone who understands the proposition can see or grasp immediately that it is true, then it is not clearly distinct from the definition of a priori, making it circular to attempt to explain a priori justification or knowledge by appeal to analyticity.)

antecedent Literally that which comes before: in a conditional claim, one of the form if A, then B, the A part is the antecedent of the conditional.

a posteriori See a priori / a posteriori

a priori / a posteriori This is a distinction concerning the reasons or justification offered for a claim. A posteriori reasons are reasons based on or derived from experience; thus "a posteriori" means the same thing as "empirical". A priori reasons are independent of experience. According to a rationalist, these reasons derive from rational insight or rational intuition, operating independently of experience, while a moderate empiricist has to say that these reasons are in some way available independently of experience but do not depend on rational insight. The claim that all bachelors are unhappy is a posteriori (or empirical), because it can only be justified by reasons derived from sense experience, but the claim that all bachelors are unmarried is a priori, because sense experience is not required for its justification; as long as you understand the claim, you can see clearly that it is true.

argument A set of claims, some of which are premises, advanced with the purpose of establishing the truth of one of the other claims, the conclusion. (Arguments may also include intermediate conclusions or lemmas, arrived at in the process of reasoning to the main conclusion.) The truth of the premises must at least appear to make the conclusion more likely to be true (than it would seem to be if the premises were false), but this need not actually be so: a fallacious argument is still an argument.

argument from illusion (sometimes called the argument from hallucination) An argument for the view that what we are directly aware of in normal cases of perception is not an externally existing material object, but instead something mental like an idea or a sense datum. The crucial premise of the argument is the claim that the character of our experience does not in itself indicate whether we are having a veridical (true) experience or not; in other words, our experience of illusions or hallucinations can seem as veridical, as genuine as an experience of an external object. The external object is clearly not the object of direct awareness in the case of hallucination (since there is no object at all) or in the case of illusion (since the real object is very different from the experienced object). But if the external object is not what we are directly aware of in these cases, and there is no experiential difference between the veridical and non-veridical experiences, then, it is argued, the immediate object of experience must be the same in all of these cases—and so cannot be an external material object. The argument from illusion is thus an argument against direct realism.

artificial intelligence (AI) Intelligence that has been constructed artificially (as opposed to the natural intelligence of humans). Many scientists (engineers and computer scientists) believe that it is possible in principle to build a computer that is genuinely intelligent (this is the program of Strong AI). A quite different view (Weak AI) holds only that computer simulations can be useful in understanding intelligence, making no claim that the computer that runs the simulation is itself intelligent.

atheism See theism.

attribute dualism See dualism.

autonomy The ability to freely determine one's own action.

axiology The general study of the nature of value, including moral value, aesthetic value, and values of other kinds.

begging the question The mistake in reasoning consisting of assuming in the premises the very thing the argument is supposed to be proving. Also called a circular argument. (In recent times, this phrase has come to be mistakenly used in the media and elsewhere to mean simply raising the question.)

behaviorism The view that bodily behavior is in some way fundamental to understanding mental states. Logical behaviorism is the view (a version of materialism) that mental states are reducible to (nothing more than) behavior and dispositions to behavior. Methodological behaviorism in psychology is the view that the proper way to study mental states is to study behavior (as opposed to appealing to introspective reports). These are distinct views, and it is possible to accept methodological behaviorism without accepting logical behaviorism.

belief The mental state of accepting or assenting to a particular proposition which is the content of the belief. If this acceptance or assent is actually present in consciousness at a particular moment of time, the belief is occurrent; if it takes the form of a standing disposition to assent if the issue is raised, the belief is dispositional. (Obviously most of the beliefs that a person has are merely dispositional at any particular moment.)

categorical imperative A moral requirement derived from reason that is binding on any rational being, that obligates one no matter what else is the case. (Contrasting term: hypothetical imperative.)

cause and effect The relation between two events whereby one, the cause, precedes and brings about the other, the effect. According to the regularity (or Humean) theory of causation, the "bringing about" is nothing more than the two events regularly occurring in that sequence. On other views, causation requires a stronger relation of necessary connection between the cause and the effect.

causal determinism The view that every event and every state of affairs is caused in every detail by prior events or states of affairs according to laws of nature; according to this view, given any particular state of the universe and given the actual laws of nature, there is only one genuinely possible future and only one genuinely possible past. A being (sometimes referred to as Laplace's demon, after the French mathematician Pierre Laplace) who knew all the laws of nature and everything true at one moment could thus infer the entire history of the universe. The term is also used in such a way that it can be said to be true of some events (those for which there is a determining cause) and false for others.

circular A term used to describe an argument or explanation that illegitimately presupposes the very thing it is supposed to establish or account for. A circular argument is one where one of the premises is either the conclusion allegedly arrived at or something so close to that conclusion as to amount to the same thing in different words. The problem with such an argument (one that is also said to beg the question) is that anyone who does not already accept the conclusion will also (unless he is confused) not accept the premise in question, so that the argument could not give anyone a good reason to accept its conclusion. Analogously, a circular definition is one where the term being defined, or something so close to it as to amount to the same thing) is used in giving the definition. In such a case, a person who does not already understand the term being defined will be unable to understand the proposed definition, so that the definition could not help anyone to come to understand the defined term.

claim An asserted proposition, declared with the intention of stating a truth.

compatibilism The position on the free will problem (also called soft determinism) that holds that causal determinism is compatible with free will, with an action being free when it is caused in the right way (roughly by the agent's own desires or wants, and without external constraint). Compatibilists also normally hold that this condition is satisfied for most human actions, so that human beings are in fact genuinely free. (Contrasting terms: hard determinism, libertarianism.)

concept A mental entity or element that gives a person the ability to think about a certain kind of thing. For example, to have the concept of electricity is to be able to think specifically about electricity. Both the nature of concepts and how the mind comes to have them are matters of controversy. (On the latter question, see empiricism and innate.)

concept empiricism See empiricism, concept.

concrete See abstract / concrete.

conditional proposition (or just a conditional) A complex proposition (or claim) having the form if A, then B, and expressing a kind of dependence between the two component propositions A and B. The first part of the conditional (the A part) is called the antecedent, while the second part (the B part) is called the consequent. Philosophers often use conditionals to express their views and arguments, making it important to be able to decide when a conditional is true and when it is false. Unfortunately, this is a matter of some difficulty. The one clear fact is that a conditional whose antecedent is true and whose consequent is false is itself false, since that is the one case that the conditional clearly guarantees will not happen. Logicians and philosophers have introduced an interpretation of the conditional (sometimes referred to as the material conditional), under which a conditional is true in the other three possible cases (both antecedent and consequent true, both false, and false antecedent with true consequent), and it is this construal of the conditional that is employed in symbolic logic. But it is clear that conditionals in ordinary language are sometimes true and sometimes false in these three cases, with the reason being that their truth depends (not at all surprisingly) on the relations (such as, especially, causation) between the events described by the antecedent and consequent and not just on the truth or falsity of these claims. (Consider, for example, the conditional claim "if George Washington had been an elephant, then he could have barked like a dog". It is a silly claim to be sure, but according to a natural interpretation of it, the claim is false, since elephants cannot bark like dogs. But according to the material conditional interpretation, the claim is true, because the antecedent is false.)

contingent See necessary / contingent.

consequent Literally, that which follows: in a conditional claim, one of the form if A, then B, the B part is the consequent of the conditional.

consequentialism The view that whether an action is right or wrong is entirely determined by the value (good or bad) of the results or consequences of the action. Utilitarianism is the main variety of consequentialism. (Contrasting term: deontological.)

contradiction, contradictory A contradiction is a proposition that is necessarily false just because of the logical properties of the proposition itself, with the clearest case being a proposition that explicitly asserts and denies the very same thing (today is Tuesday and today is not Tuesday), often referred to as an explicit contradiction. (An implicit contradiction is a proposition that can be turned into an explicit proposition by providing correct definitions for some of its component terms (John is a bachelor and John is married).) Sometimes the term contradiction is used loosely to refer to any necessarily false proposition (in which case being contradictory could not explain necessary falsehood). Two individually non-contradictory propositions are contradict each other if and only if the conjunction of the two is contradictory (in which case the truth of either one is sufficient to prove the falsity of the other. The principle of contradiction (sometimes also referred to as the principle of non-contradiction is the logical principle that a contradiction can never be true.)

corporeal Made entirely of bodily or physical or material components.

counterexample An example or particular case which shows that some particular claim is false; if the claim in question is, for example, that all bachelors are unhappy, then coming up with a specific example of a happy bachelor would show that the claim is false, and thus would be a counterexample.

deductive argument An argument whose premises purport to guarantee the truth of the conclusion (see argument).

deontological A view which holds that the rightness or wrongness of an action depends on something other than the value of the consequences of the action. Deontological views may say, for example, that rightness or wrongness depends on the form of the action or the principle that it conforms to. Such views often stress duties or rights as the source of rightness or wrongness.

determinism see causal determinism, hard determinism, compatibilism

dialectic A term used to describe the characteristic structure of philosophical reasoning and argument, involving problems or questions, views or positions on those problems, arguments for those views, responses to those arguments, replies to those responses, etc.; and also arguments against those views, responses to those arguments, replies to the responses, etc. Philosophical progress or discovery may sometimes consist in finding a definitive solution to a philosophical problem, but more often in adding new ingredients to this dialectical structure: a new argument or objection, a new response to an old argument or objection, a further reply, etc.; or (more rarely) a new position on an old problem; or (rarest of all) a genuinely new problem or issue.

direct realism (also called naïve realism) The view that the direct or immediate objects of sense perception are common-sense physical objects (and that these objects have at least largely the features they are perceived to have). (Contrasting term: representative realism.)

distributive justice Justice as it pertains to the distribution of valuable commodities among people.

double effect, law (or principle) of The view that there is a morally relevant difference between actions whose bad consequences are intended and other actions whose bad consequences are unintended either as an end or as a means to an end, though still foreseen. Compare, for example, the following two actions: (1) a doctor performs an operation on a pregnant woman to remove a cancerous tumor, killing the fetus as a foreseen but unintended side effect; and (2) a doctor performs an abortion on a pregnant woman whose life is threatened by the pregnancy. According to the standard version of the principle, (1) is permissible (because the death of the fetus is not intended), but (2) is not (because the death of the fetus is a means to an end and so intended). And this is so even in the version of case (2) where both mother and fetus will die if nothing is done and where the fetus is too immature to survive if surgically delivered.

dualism The metaphysical view that mind and body (or mental states and bodily states) are in some way fundamentally different and distinct from each. (Contrasting term: materialism.) According to substance dualism, the mind and the physical body (including the brain) are two different entities or substances, each having their own distinctive properties. Bodies have physical properties like size, weight, spatial position, etc.; whereas minds have none of these features, but are instead immaterial and spiritual in character. A second, importantly different version of dualism is attribute or property dualism, according to which there are two irreducibly different kinds of properties or attributes or features, physical features (like the ones listed earlier) and mental or spiritual features (consciousness and more specific conscious properties), but both belonging to the same thing or substance. This thing or substance that has both kinds of properties is what we refer to as the body (or perhaps the brain); but since it has both kinds of properties, it is in itself neither purely physical nor purely mental or spiritual in nature. (A further issue for both versions of dualism is what causal relations, if any, there are between the two kinds of substance or the two kinds of properties, with interactionism, epiphenomenalism, and parallelism being the main alternatives.)

duty A duty is an obligation, something that a person is required to do. If something is a legal duty, then the person is required by law to do it; if something is a moral duty, then the person is required by morality to do it. Kant distinguished between imperfect duties, requirements that have some flexibility about how to satisfy them; and perfect duties, requirements that have no such leeway. So, for example, if I have an imperfect duty to help others, then just exactly how I satisfy that duty (who I help and when I do so) is to some extent at least up to me; while if I have a perfect duty to keep my promises, then I must always keep all of my promises.

egalitarianism The general view that all people should be treated equally. More specifically, the view with regard to distributive justice is that every person should have an equal share of income, wealth, property, and the like.

eliminativism The view that minds or mental states simply do not exist, in spite of the fact that we think that they do (as, for example, one could have said that witches did not exist, even though people involved in the Salem witch trials surely thought that they did). The usual eliminativist view is that mental states and properties are postulated by a plausible but ultimately unsatisfactory theory of human behavior: folk psychology.

entail Premises entail a conclusion when the truth of the premises guarantees the truth of the conclusion; or equivalently, where it is not possible in the logical or metaphysical sense for the premises to be true and the conclusion false.

empirical Depending on sense experience; if a claim or statement is empirical, then the justification of the claim depends on sense experience; if a question is empirical, then the correct answer to the question is determined by sense experience. (See a priori / a posteriori.)

empiricism A view that emphasizes the cognitive role of sense experience. Concept empiricism is the view that all concepts (or ideas) are acquired by abstraction from sense experience. (Contrasting term: innate.) Justificatory empiricism, on the other hand, is the view that all claims (or, in some versions, all claims that are not analytic or mere definitional tautologies) must be justified by appeal to sense experience. (Contrasting term: rationalism.)

empiricism, concept. See empiricism

empiricism, justificatory. See empiricism

empiricism, moderate The version of justificatory empiricism which holds that while there is both a priori and a posteriori (or empirical) justification for claims, a priori justification pertains only to claims that are analytic (or are tautologies)—so that there is no synthetic a priori justification or knowledge. (Contrasting term: rationalism, radical empiricism.)

empiricism, radical The version of justificatory empiricism which holds that there is no a priori justification for claims of any sort—so that all justification is empirical. (Contrasting terms: rationalism, moderate empiricism.)

epiphenomenalism The version of dualism in the philosophy of mind which holds that the body (or bodily properties) causally affects the mind (or mental properties), but that the mind does not causally affect the body. (Contrasting terms: interactionism, parallelism.)

epistemology The philosophical study of the nature of knowledge and of how it is acquired and justified.

equivocation A mistake in reasoning where a word or term has one meaning at one point in an argument and a different meaning at another point in the argument, so that the argument appears to be cogent but really is not. A simple example: all banks are next to bodies of water; the First National Bank is a bank; therefore, the First National Bank is next to some body of water.

ethical egoism The view that morality requires only that people act so as to promote their own self-interest, instead of requiring people to act so as to promote the interest of someone else (which would be an altruistic act). (Contrasting term: psychological egoism.)

ethics The philosophical study of morality: of right and wrong behavior, and especially of how people ought to behave in relation to each other.

eudaimonia The Greek term for the most desirable state for an individual person. It is sometimes translated as "happiness" and sometimes instead as "flourishing".

evil, problem of The objection to the existence of God (conceived as omnipotent and morally perfect) that appeals to the existence of evil and suffering in the world, and especially to the large amount of evil and suffering that the world contains. As conceived, God would apparently be both able and willing to prevent evil, so why then does evil exist? (See theodicy.)

explanatory argument (or inference) Sometimes called an inference to the best explanation or an abductive argument, this is a form of argument in which one concludes that something is (probably) the case because it is the best explanation of something else that one believes to be true. Astronomers used this kind of argument when they argued that there was a ninth planet beyond Neptune: the reasoning appealed to the fact of the perturbations in Neptune's orbit, claimed that the best explanation for such disturbances in Neptune's orbit was the existence of another planet, and so concluded that such a planet probably exists (the one we now know as Pluto).

first cause argument An argument for the existence of God based on the claim that everything must have a cause, but that the chain of causes cannot go backwards to infinity, and so there must be some first cause (which is claimed to be God).

formal Devoid of specific content, pertaining only to the form or structure of something. If the input to a computer system is formal, then the system operates only on the aspects of the input that are independent of its meaning or content (for example the shape or structure of the symbols employed).

functionalism A recent view in the philosophy of mind which identifies mental states by their causal role in relation to inputs, outputs, and other mental states. Such a definition does not require that the specific state that occupies such a causal role be material in character, or that it be immaterial, but allows it to be either. Functionalists standardly believe, however, that the states that actually occupy the causal roles in normal humans are states of the brain and so material.

hard determinism The position on the free will problem that denies the existence of free will on the grounds that freedom is incompatible with the causal determination of human actions. The most straightforward version of hard determinism asserts the truth of causal determinism and then concludes on this basis that freedom, being incompatible with causal determinism, does not exist. But there is a second view that is also sometimes referred to as hard determinism: this view accepts the possibility of random or chance events, but argues that randomness is also incompatible with freedom; since causal determination and randomness are the only two possibilities, this second view claims, freedom still does not exist. (Contrasting terms: compatibilism, libertarianism.)

hedonism The view that pleasure or happiness is the only thing that is intrinsically good. As this suggests, hedonists tend to regard pleasure and happiness as the same thing, but this is in fact quite dubious: pleasure is usually thought of as a kind of sensation, while happiness is a more complicated and demanding state of mind in which pleasant sensations play only a minor role at best.

hedonistic utilitarianism The version of utilitarianism that holds that utility is to be understood entirely in a hedonistic way, and thus in terms of pleasure or happiness. Both Jeremy Bentham and John Stuart Mill are hedonistic utilitarians. (Contrasting terms: ideal utilitarianism, preference utilitarianism.)

hypothetical imperative A rational requirement that derives from a want or desire that a person happens to have For example, if you want to become a first-rate pianist, then you have a rational requirement to practice. (Contrasting term: categorical imperative.)

idealism The metaphysical view that that reality consists only of minds or spirits and mental contents. This means that there are no independently existing material things (so the view could also be called immaterialism). Instead what common sense refers to as material objects of various kinds are nothing more than patterns of ideas or experience. See also phenomenalism.

ideal utilitarianism The version of utilitarianism that holds that utility involves many different kinds of intrinsically good things (and correlative bad things), not just pleasure or happiness. Knowledge is a good example of something that would be regarded as an intrinsic good by many ideal utilitarians, but that is clearly distinct from pleasure or happiness. (A further issue is whether intrinsic goods are all states of mind of one sort or another.) (Contrasting terms: hedonistic utilitarianism, preference utilitarianism.)

idea For Locke, whatever one is immediately aware of when one thinks. This seems to include both specific sensations or sense-data and general concepts.

identity theory, the The view in the philosophy of mind (one version of materialism) according to which any given sort of mental state is identical to exactly one kind of brain state. In contrast to logical behaviorism, this identity is claimed to be contingent and discovered by empirical investigation, rather than being a consequence of the meaning of mental state concepts. The identity theory is sometimes described as "type-type materialism" (or physicalism) because each type of mental state is identical with a specific type of physical state; in contrast, according to functionalism, a given type of mental state might be realized by different physical states in different kinds of creatures or even in different human beings ("token-token materialism", because each specific instance of a mental state is identical with some specific instance of a physical state).

ignoratio elenchi A mistake in reasoning that involves arguing for a conclusion that is irrelevant to the original issue—also missing the point.

illusion, argument from See argument from illusion.

immaterialism See

imperfect duty See duty.

inductive argument The sort of argument (also called enumerative or instantial induction) that infers from many specific cases (many cases of A that are also cases of B, and perhaps also some cases of A that are not cases of B) to a general claim formulated in the same terms (where there are no exceptions, that all A's are B's; or, where there are exceptions, that some specific percentage of A's are B's). More generally, any sort of reasoning where the premises provide good but not conclusive support for the truth of the conclusion. (In this more general sense but not in the narrower one, an explanatory argument would be an instance of inductive reasoning.)

inference The transition from a set of premises to a conclusion.

innate Implanted at birth, rather than acquired through subsequent experience. An innate idea (or concept) would be one that is somehow present in a person's cognitive abilities at birth, rather than being acquired via abstraction from experience. (The contrasting view is concept empiricism.) Such an idea might be one that infants are actually conscious of or, more plausibly, one that required to be activated or "triggered" by experience before emerging into consciousness—with the difference from concept of empiricism being that the triggering experience would not need to be one from which the idea in question could be derived by abstraction. Earlier proponents of innateness (such as Rene Descartes) tended to think of innate ideas as being implanted by God, but some more recent philosophers have appealed instead to evolution.

insight, rational See rational insight.

instrumental good See intrinsic good / instrumental good.

intentional content See intentionality.

intentionality The general property of being about something that is possessed by some but not all mental states and also by language. A thought concerning polar bears is an intentional state (because it is about polar bears), whereas neither a free floating state of anxiety nor a sensation of redness or pain is about anything. (A sensation of redness is a sensation of a certain distinctive kind, but is not in itself about anything.)

interactionism The version of dualism in the philosophy of mind that holds that there is causal interaction between immaterial minds or mental states and material bodies or bodily states: that each can and does causally affect the other. (Contrasting terms: epiphenomenalism, parallelism.)

intrinsic good / instrumental good Something is an intrinsic good (or has intrinsic value) if it is good in itself, good for its own sake, independently of anything else or of any further purpose; whereas something is an instrumental good if it is good as a means to something else. Happiness is the most obvious example of something that is intrinsically good; whereas, for all but misers, money is merely an instrumental good: it is good only for what it can get you, not for its own sake. It is possible for something to be good in both ways: knowledge is an example of something that has often claimed to be intrinsically good, but which is instrumentally good as well.

intuition, rational See rational insight.

invalid See valid.

justification In epistemology, a reason or basis for thinking that some claim or view is true; in ethics, a reason to think that an action is right.

justificatory empiricism See empiricism, justificatory.

knowledge The proper definition or analysis of knowledge has been a matter of ongoing controversy in recent philosophy. According to what is often referred to as "the traditional conception of knowledge", knowledge is belief that is both adequately justified and true. (Thus a lucky guess, even if true, does not count as knowledge.) The problem with this definition, raised by Edmund Gettier, is that there seem to be cases where all three of these conditions are satisfied, but which do not seem to be genuine cases of knowledge. Intuitively, these are cases where the belief is true, not in the way that the justification would suggest, but in some accidental or unexpected way. In perhaps the most widely discussed example, you have excellent reasons for thinking that a specific one of your co-workers (Mr. Nogot) owns a Ford automobile, and come to believe on that basis the more general claim that one of your co-workers owns a Ford. In fact, however, Nogot does not own a Ford (your evidence is somehow mistaken or misleading), but another one of your co-workers (Mr. Havit) does own a Ford—though you have no reason at all for thinking that this is so. In this situation, your general belief that one of your co-workers owns a Ford seems to be both justified (by you evidence about Nogot) and true (because of Havit), but still intuitively not to be an instance of knowledge. Many solutions have been offered for this "Gettier problem", involving modifications of one of the three original conditions or else the addition of a fourth condition, but none have received general acceptance. (One thing worth noting is that the possibility of "Gettier cases" depends on the assumption that it is possible for a belief to be justified to the degree that is adequate for knowledge and still be false—this is what allows it to also be true in an accidental or unexpected way.)

libertarianism (1) In metaphysics, the position on the free will problem which holds both (a) that free will is incompatible with causal determination and (b) that free will genuinely exists (and thus that causal determinism is false for at least some human actions). Thus characterized, the general libertarian view is compatible with the idea that a free action is simply a random or chance occurrence, but virtually all recent libertarians have also held that freedom is incompatible with randomness. Thus a libertarian is committed to their being a third alternative with regard to the production of human actions, one that is distinct from both causal determination and randomness. (Contrasting terms: hard determinism, compatibilism.) (2) In political philosophy, the view that emphasizes the importance of individual liberty and individual rights, and on this basis advocates severely limited government.

logical behaviorism See behaviorism.

logical positivism A philosophical movement of the early to mid twentieth century dominated by a scientific outlook, which advocated both moderate empiricism and the view that only claims that can be verified by sense experience or else reduced to logical tautologies are meaningful.

materialism The metaphysical view (also referred to as physicalism) that all that exists is material, that every event, object, property or state is entirely material, that there are no immaterial entities, aspects, or properties; in the philosophy of mind, the view that minds and mental states can be somehow reduced to or entirely accounted for in material or physical terms (so that dualism is false).

metaphysics The philosophical study of the ultimate nature and fundamental constituents of reality; there are metaphysical questions about, for example, the nature of space and time, the nature of causation, whether everything is material, whether human actions are free or causally determined, whether universals exist, and so on.

moderate empiricism See empiricism, moderate.

moral evil The evil caused by human actions (or, possibly, by the actions of other rational creatures such as demons or angels) instead of by natural events such as hurricanes or tornadoes (see natural evil).

moral nihilism The view that there are no true moral claims of any sort (and so that no action is ever morally right or morally wrong). Moral nihilism does not, of course, deny that people often make moral claims and have moral opinions; it just says that none of these claims or opinions are ever genuinely true or correct. (Contrasting terms: moral objectivism, moral relativism.)

moral objectivism The view that there are at least some moral claims that are objectively true, true independently of any limited perspective or point of view (also referred to, somewhat misleadingly, as moral absolutism). Two possible sorts of misconception about this view are worth noting: (a) The objective moral truths need not be simple (never tell a lie), but may instead refer to circumstances in complicated ways (never tell a lie unless telling the truth will do more harm than good, and it is impossible to avoid saying something). (b) Moral objectivism does not claim that there are objective moral truths on every subject about which moral opinions have been offered; in particular, it is possible that even though moral objectivism is true, there are no objective moral truths pertaining to some or all aspects of sexual morality. (Contrasting terms: moral nihilism, moral relativism.)

moral relativism The view that there are moral truths, but that moral truth is not objective, but instead is relative to the individual (different moral truths for different individuals), to the community (different moral truths for different communities), or to something else (cultures, historical epochs, etc.). (Contrasting terms: moral nihilism, moral objectivism.)

moral virtue A morally valuable character trait. Examples would include such things as courage, temperance, kindness, and honesty.

naïve realism See direct realism.

natural (or physical) evil The evil caused by natural events (such as hurricanes or tornadoes), rather by human actions (see moral evil). The evil resulting from diseases, birth defects, and the like also counts as natural evil as long as it is not deliberately produced by human beings.

necessary / contingent In the strongest and most common sense (logical or metaphysical necessity), a necessary truth is a proposition that could not have been false, that is true no matter what the actual course of events in the world happens to be, that is true in any possible world or situation (and a necessary falsehood is a proposition that could not have been true); while a contingent truth is a proposition that is true but might have been false, one whose truth or falsity depends on the actual course of events in the world, one that is true in some possible worlds or situations and false in others (and a contingent falsehood is a proposition that is false but might have been true). For example, true mathematical claims (such as 2 + 2 = 4) are necessary truths, as are the various truths of logic (such as either today is Tuesday or today is not Tuesday); while claims like George W. Bush is President in 2004 or the population of the U.S. is larger than the population of France are contingent, as are most other ordinary claims about the world. Contingent events are events described by contingent propositions, and so events that might or might not occur. (For a related but weaker use of these terms, see necessity, causal or nomological.)

necessary condition / sufficient condition If X is a necessary condition for Y, then Y cannot happen or obtain unless X happens or obtains; whereas if X is a sufficient condition of Y, then Y cannot fail to happen or obtain if X happens or obtains. For example, oxygen is a necessary condition for fire (because there can be no fire unless there is oxygen), but oxygen is not a sufficient condition for fire (because there isn't fire every time and every place where there is oxygen). Whereas having a knife driven through one's heart is a sufficient condition for death (anyone to whom this is done dies), but not a necessary condition (there are lots of other ways to die). Some conditions may be both necessary and sufficient: being an unmarried adult male is both necessary and sufficient for being a bachelor: necessary, because any bachelor must have these properties; sufficient, because these three properties are all that it takes to be a bachelor.

necessity, causal or nomological A grade of necessity (and contingency), weaker than logical or metaphysical necessity (see necessary / contingent), that results from laws of nature rather than laws of logic and metaphysics. A proposition is causally or nomologically necessary if it could not have failed to be true without altering the actual laws of nature that govern the world, and thus is true in any possible world obeying those same laws of nature; while a proposition is causally or nomologically contingent if both its truth and its falsity is compatible with the actual laws of nature (and thus if it is true in some possible worlds obeying those laws of nature and false in others). The same terms are also applied to the events described by such propositions. For example, the gravitational attraction between two bodies varies with the square of the distance between them is causally or nomologically necessary (but not logically or metaphysically necessary, since there are possible worlds with different laws of gravitation). Whereas many ordinary claims about the world (it is not raining today, there are pine trees in Washington state, gold is more expensive than lead, and so on, and so on) are contingent in both the causal or nomological sense and the logical or metaphysical sense. (Anything that is logically or metaphysically necessary is also causally or nomologically necessary: if there is no possible world in which it is false, then it follows trivially that there is no possible world with the same laws of nature in which it is false.)

normative Having to do with norms or rules or standards specifying the way that something properly ought to be.

objection A reason to reject a claim or view or argument.

objectivism The view that the subject matter in question is what it is independently of what anyone believes; for example, ethical objectivism is the view that there are facts about what is morally required that don't depend on what humans happen to believe.

Ockham's (or Occam's) razor An intellectual presumption in favor of simplicity or theoretical economy (sometimes called the principle of parsimony), by which one is advised to accept only those entities genuinely required to explain or account for something. Named after William of Ockham (c. 1285-1347), a medieval philosopher.

occasionalism See parallelism.

original position In John Rawls's account of justice, this is the hypothetical starting point, in which people, operating behind a "veil of ignorance" with respect to their own position in society, natural talents, and other features, choose the correct principles of justice.

panpsychism The view that all of reality is in some sense made up of mental stuff, but not necessarily of human mentality, since human mentality might be just an instance of a more general type of thing. This is different from idealism: whereas the idealist reduces material things to patterns of experience, the panpsychist grants them an independent existence, but holds that they are in some way still ultimately psychical in character.

parallelism The version of dualism in the philosophy of mind which holds that there is no causal relation between immaterial minds or mental states and material bodies or bodily states in either direction, that the mental and physical realms have no causal influence at all on each other, despite seeming to interact. The main versions of parallelism explain the appearance of interaction by appeal to divine intervention, either a pre-established harmony established at the beginning of creation (so that mind and body are like two perfect clocks, running side by side but neither influencing the other) or constant divine intervention to keep the two realms in agreement with each other (occasionalism).

perfect duty See duty.

person For philosophers, this is not a biological category but a moral one: a person is a being (or any sort or species) that by virtue of its nature and characteristics should be accorded the sort of respect and rights ordinarily ascribed to normal adult human beings. Thus some animals might turn out to be persons, some aliens or extraterrestrials might also be persons, and some humans (for example, those in a permanent coma) may not in fact be persons.

phenomenalism A version of idealism which holds that the common-sense material objects of our experience (things such as tables, trees, and mountains) are really nothing more than systematic patterns of sensory experience—what John Stuart Mill calls "permanent possibilities of sensation".

phenomenal properties Those properties of mental states that have to do with the way the mental state seems or feels from the inside, determining "what it is like" to experience that mental state; the experience of a headache, for example, has a very different phenomenal property (or quale, plural qualia) from the experience of tasting a lemon, and both of these are very different from the experience of a patch of red color.

physical evil See natural evil.

physicalism See materialism.

possible A proposition is possibly true, in either the strong logical or metaphysical sense or the weaker nomological sense, if it is not necessarily false in the correlative sense. A situation or event is possible in one of these senses if the proposition describing it is possible in that same sense. A possible world is a world whose complete description is possible in one or the other of these senses (thus there are logically or metaphysically possible worlds and causally or nomologically possible worlds, with the latter being included in the former).

pre-established harmony See parallelism.

preference utilitarianism The version of utilitarianism which holds that utility consists in the satisfaction of preferences (so that in the act utilitarian version, the morally right action would be the one that led to the maximal amount of preference satisfaction, measured by both the number and the strength of the preferences satisfied).

premise See argument.

primary quality / secondary quality Primary qualities are those qualities that any object must have, no matter how much change it endures or whether it is being perceived or not: for example (according to John Locke), size (extension), shape (figure), motion, number, and solidity. A further claim is that our ideas or perceptions of primary qualities accurately depict their nature as they exist in objects. Secondary qualities, on the other hand, are mere powers (causal capacities) of the object to systematically produce ideas in us, ideas, for example of colors, sounds, tastes, and smells, so that there is no quality actually in the object like the one that is represented in our experience. Thus, for example, a ripe apple genuinely has the distinctive shape and size that we experience it to have, but it does not have any property like the red color we experience (though it does have some property—presumably some combination of the primary qualities of its surface—in virtue of which it systematically causes experiences of red in creatures like us.)

principle of sufficient reason (PSR) The metaphysical principle that for everything that happens and for everything that exists, there must be a reason or explanation or cause for it being the way that it is, instead of some other way or no way at all.

property dualism See dualism.

proposition An abstract object capable, in virtue of its meaning or content, of being true or false. A proposition is what is expressed by a declarative sentence, and on the most standard view, can be expressed by many different sentences from different languages; for example, the sentences "Snow is white", "Das Schnee ist weiss", and "La neige est blanche" all express the same proposition. Propositions can also be entertained in thought in various ways: believed, doubted, desired to be true, feared to be true, etc. Any act of thought that has a proposition as its object or content is called a propositional attitude.

psychological egoism The view that as a matter of psychological fact, a human being is capable of being motivated only by his or her own selfish interests, that humans are incapable of genuine acts of altruism (acts whose goal is to further the interest of someone else).

psychophysical laws Laws describing regular relations between mental or psychological events and material or physical events.

quale (plural qualia), See phenomenal property.

question-begging See begging the question.

radical empiricism See empiricism, radical.

rational insight The alleged direct or immediate grasp, without any appeal to experience, of the truth or necessity of a proposition. (Also referred to as rational intuition.) According to rationalism, such insight is the basic source of a priori justification and knowledge.

rational intuition See rational insight.

rationalism Broadly, the epistemological view that reason is a significant source or basis for knowledge (in the most extreme versions, now rarely if ever held, that it is the only such source or basis). As with empiricism, there are two main versions, one pertaining to the source of concepts and the other to the source of justification. A rationalist view of concept possession says that some or all concepts are innate. A rationalist view of justification says that some (a moderate version of rationalism) or all (an extreme version of rationalism) justification derives from rational insight, rather than sensory experience. Since the a priori justification of analytic claims does not require rational insight, this means that, in opposition to moderate empiricism, justificatory rationalists hold that some synthetic claims can be justified a priori.

realism A metaphysical view holding that things of some specified sort exist on their own, independently of human perceivers or knowers. Versions of realism have been held with respect to material objects, universals, moral properties or truths, theoretical entities in science (such as electrons), and many other categories of things. (Contrasting term, as regards material objects: idealism.)

reductio ad absurdum Sometimes philosophers argue against a claim by showing that it leads to a contradiction. For example, consider the claim that some bachelors are unmarried; replace "bachelor" with its definition: "unmarried adult male". Now you have a contradiction: some unmarried adult male is married; or, slightly more explicitly, some individual is both unmarried and married. If you can infer a contradiction from a claim, then you have an excellent reason for rejecting that claim and affirming its denial.

reduction Sometimes philosophers will claim that entities of one kind (for example, material objects) are really nothing more than entities of some other, seemingly different kind, or some pattern or assemblage thereof (for example, sensory experiences). Where such a claim can be successfully defended as true, the entities of the first kind have been reduced to, shown to be nothing more than, the entities of the second kind. This can be valuable for reasons of simplicity or economy (see Ockham's razor) and also because it may avoid problems or puzzles pertaining to the entities that are reduced. Though it is very doubtful whether many of them have succeeded, many attempts at reduction have been made: material objects to sense experiences (by George Berkeley and by phenomenalists), universals to features of language use, theoretical entities in science (such as electrons) to patterns of observation, mental states to material states or processes of various kinds (by the various versions of materialism), and others. (Contrasting term: realism.)

representative realism (also called indirect realism) The view (held by Rene Descartes, John Locke, and others) that external material objects are not directly or immediately perceived, but instead that our experience of such objects is mediated by an experience of mental entities or states (called "ideas" by earlier philosophers and "sense-data" by more recent ones) which (a) are caused by material objects and (b) represent or depict or resemble them. Our knowledge of the external material world is then the result of an inference starting from the character of our ideas or sense-data and concluding with beliefs about external objects.

rights In the most important sense, for a person to have a right is for there to be claim of some sort that some or all others have a correlative moral or legal duty to honor (depending on whether the right is a moral right or a legal right). Thus to have a legal right to payment for goods of some sort that have been delivered is to have a claim for payment that someone else (presumably the receiver of the goods) has a legal duty to honor. And to have a moral right not to be killed is to have a claim that one not be killed that others (in this case, normally all others) have a moral duty to honor.

rule utilitarianism See utilitarianism.

secondary quality See primary quality / secondary quality.

self-evident The property a proposition has when its very content provides a compelling reason to think that it is true. Once one understands a self-evident proposition, one can see clearly that it must be true, and that seeing constitutes a good reason for believing it. Self-evident propositions are the alleged objects of rational insight.

semantics The meaning or reference of words and also of larger linguistic structures like sentences or whole theories; also sometimes applied to concepts and to acts of thought. Semantical theory is the systematic study of such meaning and the principles that govern it. (Contrasting term: syntax.)

sense data (singular: sense datum) The direct or immediate objects of awareness in sense experience, according to those who reject direct realism on the basis of arguments like the argument from illusion. John Locke and George Berkeley speak instead of ideas, or more specifically of ideas of perception. Sense-data are usually viewed as mental entities, but some philosophers have regarded them as in themselves neither mental nor material (though the objects of mental acts of awareness or apprehension)

skepticism The view that knowledge is unattainable. One can be a skeptic about knowledge generally or only with respect to knowledge in some limited domain (for example, a skeptic about God's existence or about morality).

soft determinism See compatibilism.

solipsism The view that the only things that exist are the mind and the experiences of a single person, the one from whose point of view the claim is formulated. Solipsism is not really a view that anyone advocates (to whom would they advocate it?), but instead a pitfall into which philosophers sometimes fall by advocating other, more general views that lead to it.

substance Something capable of independent existence, as contrasted with properties or relations, which exist only in substances. Thus, for example, a material object like a table would be a substance, while properties (like its color) or relations in which it stands to other substances (like being next to several chairs) would not be. The term is also used to refer to the supposed ingredient in a substance that is distinct from all its properties (and relations) and in some way underlies or supports them (substratum is another term for this latter notion).

sufficient condition See necessary condition / sufficient condition

syntax The formal structural relations among words and larger linguistic structures; also the rules (such as rules of grammar) that govern such relations. A person who knew all of the rules of French grammar (and so could construct and identify grammatically correct French sentences), but did not understand the meanings of any French words (and so could not understand or translate any of those sentences) would know the syntax of French but not its semantics. (Contrasting term: semantics.)

synthetic See analytic / synthetic.

tabula rasa Literally, blank tablet; John Locke held the view that our minds are like blank tablets when we are born, and that experience provides the content or ideas that we subsequently use to think.

tautology Originally a proposition that is true by virtue of trivial repetition (such as tall men are tall). More generally, a sentence that is true in this trivial way or whose denial is either contradictory or leads immediately to a contradiction (such as either it is raining or it is not raining). Sometimes the term is construed so broadly as to include all analytic truths, but more commonly it is limited to those that are especially obvious and/or trivial.

theism / atheism / agnosticism Theism is the view that God does exist, while atheism is the view that God does not exist. Agnosticism is the view that it is seriously uncertain whether or not God exists—that the reasons or evidence on each side are fairly closely balanced, so that we cannot know whether or not such a being exists and don't have enough evidence one way or the other to hold either belief responsibly. (In earlier times, the term "agnostic" was sometimes used to describe anyone who had fairly serious doubts that God exists, whether or not such a person thought that the evidence was closely balanced—thus many who were so described are better regarded as atheists.)

theodicy An attempt to explain how and why the existence of evil in the world is compatible with the existence of an all-powerful and morally perfect God.

truth The metaphysical relation in which a proposition or claim that is accurate or correct stands to reality. This is most naturally taken to involve a relation of correspondence or agreement or accordance between the content of the proposition or claim and the corresponding part of reality (the correspondence theory of truth). But alleged problems with the correspondence theory have led some philosophers to propose various other accounts of truth, such as the coherence theory of truth (for a proposition to be true is for it to fit together with other propositions in such a way as to make up a tightly unified and cohesive system), various pragmatic theories of truth (for a proposition to be true is for it to lead to practical success of some specified sort when believed or applied), and others.

Turing machine Not a physical machine, but instead an abstract specification of a machine (invented by A.M. Turing). Such a machine has the capacity to scan a tape divided into squares, erase what is in a given square, print something in an empty square, move left or right on the tape, and change its own inner "logical state", with what it actually does at a given point being determined, according to a machine table or program, by what is on the square it is scanning and the logical state that it is in. The idea of a Turing is in effect the most general specification of a computer and can do anything that any computer can do, if given enough time and enough memory (that is, a large enough tape).

universal An abstract property or feature, such as redness or triangularity or justice. Philosophers have disputed whether universals (a) exist independently of the concrete things (particulars) that are instances of such properties (Platonic realism, the view held by Plato), (b) exist only in their instances (Aristotelian realism, the view held by Aristotle), (c) exist only in the minds of people who conceive of them (conceptualism), or (d) do not really exist at all, but are merely an illusion created by the use of words (nominalism).

utilitarianism The moral theory that the rightness of an action depends only on the goodness or badness of its consequences (this is its utility). According to act utilitarianism, the morally right action is the one out of the available alternatives that leads to the greatest overall utility, computed by adding up the good consequences and subtracting the bad ones. According to rule utilitarianism, the right action is the one prescribed by the set of moral rules whose adoption would lead to greater utility than that which would result from the adoption of any other set of rules. Different versions of utilitarianism construe the goodness or badness of consequences in different ways: see hedonistic utilitarianism, ideal utilitarianism, and preference utilitarianism.)

valid An argument is valid if it is impossible for the premises of the argument to be true while the conclusion of the argument is false. Any argument whose conclusion could be false even though its premises are true is invalid.

veil of ignorance See original position.

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