THE ESSENTIAL NATURE OF CORPOREAL SUBSTANCE – CATEGORY 1 AND CATEGORY 2 PROPERTIES – MATHEMATICAL OBJECTS AND MATHEMATICAL TRUTHS – TRIANGLES, UNICORNS, AND GOD – REALISM AND PSYCHOLOGISM (AT VII:63–5)

The Meditator's task is to reconsider the items remaining under doubt. The hypothesis of the malevolent Demon has been refuted and the Meditator's potential to expand his knowledge-set indefinitely has been established. Meditation Three revealed that clarity and distinctness were the signs of truth and that they were the only signs of truth.

Recall that the Meditator also determined in Meditation Three that his ideas of material objects with sensory qualities – qualities such as heat, cold, color, warmth, and so on – were characterized by a certain flimsiness. The following proposition:

was not clearly and distinctly perceived. At the start of Meditation Five, the Meditator has not even determined that one particularly significant corporeal thing exists, namely, his own body. Earlier, in Meditation Two, the Meditator assumed that his “body” was a hallucination induced by the Demon. While he is now certain that he is not deceived by a Demon, the feeling that he is an embodied creature that moves himself around with some effort, needs to eat, and suffers various aches and pains, may nevertheless be a kind of illusion, involving only a kind of perception1 (see above, Ch. 3 Sec. 2) of bodily sensations.