Some ethical systems are based on a belief in a god, but if there is a god, how could we know it (sans direct revelation)? Pascal's wager converts the epistemological question to a pragmatic one, asking, "What is the probability that god exists?" and, "What is the pay-off for believing?" Given that we can't know that god exists (according to Pascal), there are two possible states the universe can be in: either god exists or he doesn't. Given these two possible states, there are two possible responses: either believe he exists or don't believe. Doing the calculus, Pascal shows that whether or not god, in fact, exists, a gambler would find the odds infinitely better for believing. Even if life might be more fun without believing, when you multiply that small positive amount by infinite damnation you get an infinitely negative pay-off. Even if life might be less fun because of believing, when you multiply that small negative amount by infinite bliss you get an infinitely positive pay-off.
Can we know god exists by inference, say, the way we know that the wind is blowing, though we can't see it, by the effect it has on leaves, flags, and hats? The Stoic's 'argument from design' compared the ordered complexity and functions of a machine to the ordered complexity and functions of things in the universe and they reasoned that, just as a designer had to have been responsible for creating the machine, so too did the universe require a designer, i.e. god. The argument was attacked on many grounds, most notably by Hume and Kant. One of the biggest problems is that it posses an infinite regress, that is, if the universe is so awesome that it needs a designer-god, then the universe plus god is even more awesome and needs a super-god, and then the universe plus god plus super-god needs a super-duper-god, and so on.
