The Meditations are generally considered the starting point of modern Western philosophy, and with good reason. In this one brief text, Descartes turns many Aristotelian doctrines upside down and frames many of the questions that are still being debated in philosophy today. Among other things, Descartes breaks down the Aristotelian notion that all knowledge comes via the senses and that mental states must in some way resemble what they are about. In so doing, he develops an entirely new conception of mind, matter, ideas, and a great deal else besides.