Existence and 'I Am'

Proposition 1: We only be absolutely certain of anything as long as we know that we exist

Proof: This Proposition is self-evident.

A person who does not know that he exists will not know that he is a being affirming or denying.

We can affirm or deny many things even if we ignore the fact that we exist. But in this case, everything can be doubted*.

Proposition 2: ‘I am’ is self-evident.

Proof: If this is denied, then ‘I am’ can only be known through something else. The knowledge and certainty of that something will be prior to the statement ‘I am’ (Ax. I). But this is absurd (Prop. I ). Q.E.D.

Proposition 3: ‘I am’, insofar as the ‘I’ is a thing consisting of body, is not a first principle and is not known through itself

Proof: There are certain things that make us doubt the existence of our body (Ax. 2).

Therefore, (Ax. I) we shall not attain certainty of this except through the knowledge and certainty of something else that is prior to it in knowledge and certainty.

Therefore the statement ‘I am’, insofar as T am a thing consisting of body, is not a first principle and is not known through itself. Q.E.D.

Proposition 4: ‘I am’ cannot be the first known principle except insofar as we think.

Proof: The statement ‘I am a corporeal thing, or a thing consisting of body’ is not a first-known principle (Prop. 3). I am not certain of my existence insofar as I consist of anything other than mind and body.

For if we consist of anything different from mind and body, this is less well known to us than body (Ax. 3). Therefore ‘I am’ cannot be the first known thing except insofar as we think. Q.E.D.

Corollary: Mind, or a thinking thing, is better known than body.

But for a fuller explanation read Part 1 of the Principia Arts. II and 12.

Scholium: Everyone perceives with the utmost certainty that he affirms, denies, doubts, understands, imagines, etc., or that he exists as doubting, understanding, affirming, etc.- in short, as thinking. Nor can this be called into doubt.

Therefore the statement ‘I think’ or ‘I am, as thinking’ is the unique (Prop. 1) and most certain basis of all philosophy.

In order to achieve the greatest certainty in the sciences, our aim and purpose can be only to:

• deduce everything from the strongest first principles and
• make the inferences as clear and distinct as the first principles

We must consider as true everything:

• that is equally evident to us and that we perceive with the same clearness and distinctness as the already discovered first principle
• that so agrees with this first principle and so depends on it

But to proceed with the utmost caution in reviewing these matters, at the first stage I shall admit as equally evident and equally clearly and distinctly perceived by us only those things that each of us observes in himself insofar as he is engaged in thinking.

Such are, for example, that he wills th is or that, that he has definite ideas of such-and-such a kind, and that one idea contains in itself more reality and perfection than another-namely, that the one that contains objectively the being and perfection of substance is far more perfect than one that contains only the objective perfection of some accident, and, finally, that the idea of a supremely perfect being is the most perfect of all.

These things, we perceive not merely with equal sureness and clarity but perhaps even more distinctly; for they affirm not only that we think but also how we think.

Further, we shall also say that those things that cannot be doubted without at the same time casting doubt on this unshakable foundation of ours are also in agreement with this first principle.

For example, if anyone should doubt whether something can come from nothing, he will be able at the same time to doubt whether we, as long as we are thinking, are. For if I can affirm something of nothing- in effect, that nothing can be the cause of something-I can at the same time and with the same right affirm thought of nothing, and say that I, as long as I am thinking, am nothing.

This is impossible. Therefore, it will also be impossible for me to think that something may come from nothing.

With these, I have decided to list here those things that at present seem necessary to us for future progress, and to add to the number of axioms.

These are set forth by Descartes as axioms at the end of his “Reply to the Second Set of Objections,” and I do not aim at greater accuracy than he.

However, not to depart from the order we have been pursuing, I shall try to make them somewhat clearer, and to show how one depends on another and all on this one first principle, ‘I am, while thinking’, or how their certainty and reasonableness is of the same degree as that of the first principle.