Synopsis of the Six Following Meditations

Descartes provides a brief account of what each of the six meditations achieves. The First lays the grounds for universal doubt — by showing that the senses sometimes mislead, that dreaming is indistinguishable from waking, and that an evil deceiver might be corrupting even mathematical intuitions. The purpose of the doubt is not skepticism but the discovery of what cannot be doubted at all. The Second finds that even in total doubt the mind must exist, since doubting is itself a form of thinking. It also shows that the mind knows itself more directly than it knows any body — the wax example demonstrates this. The Third demonstrates God's existence from the nature of the idea of God in the mind: the idea represents an infinite, perfect being; nothing finite and imperfect could be the adequate cause of that idea; therefore an actually existing perfect being must have caused it.

The Fourth explains how error arises in a world created by a perfect and non-deceiving God: not because God gave us defective faculties but because we misuse our freedom by assenting to propositions we do not clearly perceive. The Fifth gives a new proof of God's existence from the concept of essence — existence belongs to God's nature the way three angles equal to two right angles belongs to a triangle — and shows that the truth of clear and distinct perceptions cannot be doubted once God's existence is secure. The Sixth proves that material things exist (since God cannot systematically deceive us about the powerful inclination we have to believe in them) and argues for the real distinction between mind and body.

A note about what the book does not prove: the immortality of the soul. Many readers expect this. Descartes says the distinction of mind from body is established, but immortality requires further premises from physics — premises that the Meditations does not supply. The Synopsis is an honest map of what lies ahead, and it is honest about the limits as well as the achievements.