ABSTRACT
The inference Descartes drew here is pretty dubious. He may have been unable to doubt that he exists, and his perception that he does exist may have been clear and distinct; but his ignorance of his nature as a thinking thing was sufficiently great at this stage that he was hardly warranted in assuming that he would not be "assured" that what he perceived is true if it could happen that what he clearly and distinctly perceived is false. What could he know about the conditions in reality required to assure him about something? The answer should be "nothing." If he knew what he will eventually attempt to prove - that God exists, is his creator, and is not a deceiver - he may have been able to make a plausible case for this assumption; for a false assurance, or conviction, in a matter like this would then have been arguably a defect in his nature attributable to a deceptive (or at least imperfect) creator. As it was, Descartes' general rule is a very dubious guide or principle for a cautious, critical thinker. 29
What are the properties of clarity and distinctness in an idea? Descartes defined them in his Principles of Philosophy:
I call a perception "clear" when it is present and accessible to the attentive mind - just as we say that we see something clearly when it is present to the eye's gaze and stimulates it with a sufficient degree of strength and accessibility. I call a perception "distinct" if, as well as being clear, it is so sharply separated from all other perceptions that it contains within itself only what is clear.30
