Suppose that there be a machine, the structure of which produces thinking, feeling, and perceiving; imagine this machine enlarged but preserving the same proportions, so that you could enter it as if it were a mill. This being supposed, you might visit its inside; but what would you observe there? Nothing but parts which push and move each other, and never anything that could explain perception.
The point of Leibniz's thought experiment is that thinking, feeling, and perceiving cannot be explained by mechanism, by mere parts and movements of parts (as claimed by materialists). In other words, there is more to the mind than the brain (as claimed by dualists). What "more" could this be? Leibniz's explanation involves a sort of harmonious orchestration by God of simple elements (monads) that bond together and form composites (matter).
But we know today that mental states have measurable correlates - electrical and biochemical changes - in the brain. And indeed, if the mind were truly something separate from the brain, why would brain injuries affect mental features like reason, emotion, and consciousness? So perhaps there isn't more to the mind than the brain.
And yet a brain scan can indicate only that we're thinking, not what we're thinking. Furthermore, the actual experience of thinking is not at all like the corresponding brain state.
Sources:
Gottfried Wilhelm von Leibniz. Monadology. Section 17. 1714. Paul Schrecher and Anne Martin Schrecher, trans. Indianapolis: Bobbs-Merrill, 1965. 150.
Peg Tittle. What If ...Collected Thought Experiments in Philosophy. Part 2, Philosophy of Mind. New York: Pearson Education, Inc., 2005. 48-49.
|