Liberation from All Doubts

Finally, to remove all doubt, he asks into the nature of the most perfect Being, and whether such exists.

He realizes that there exists a most perfect Being, by whose power all things are produced and preserved.

His nature is contrary to that of a deceiver.

This removed the reason for doubting the cause of himself.

This made him realize that the faculty of distinguishing true from false was not given to him by a supremely good and truthful God in order that he might be deceived.

And so mathematical truths, or all things that seem to him most evident, cannot be in the least suspect.

To remove the other causes for doubting, he goes on to ask how we sometimes err.

He discovers that error arises from our using our free will to assent even to what we have perceived only confusedly.

He was immediately able to conclude that he can guard against error if he only accepts what he clearly and distinctly perceives.

Everyone can do this because everyone has the power to control the will and thereby restrain it within the limits of the intellect.

But in our earliest days, we have been imbued with many prejudices from which we are not easily freed.

To be freed from them, he enumerates all the simple notions and ideas from which all our thoughts are compounded.

He examines them one by one, so that he can observe in each of them what is clear and what is obscure.

In this way, he easily discovers:

• the real distinction between soul and body
• what is clear and what is obscure in the deliverance of our senses

• dreaming from waking.

Some people argue that the existence of God is not self-evident to us, and so we can never be certain of anything, even of God’s existence. This leads to uncertain premises of which nothing certain can be concluded.

To remove this difficulty, Descartes replies that:

• we do not know whether the author of our origin has created us to be deceived.

• but it does not follow that we can doubt those things that we understand clearly and distinctly through themselves or through a process of reasoning

Therefore, the existence of God can be known not through itself but only through something else.

Yet, we can nevertheless attain a knowledge of God’s existence if we carefully attend to all the premises from which we conclude it. See Principia Part 1, Article 1 3, and “Reply to Second Objections,” No. 3, and at the end of the “Fifth Meditation.”

However, some do not find this reply satisfactory, so I shall give another*.

When we were speaking of the sureness of our existence, the proof of our existence came from us perceiving things through our mind’s eye.

This proof was in force whether we were:

• considering our own nature, or
• imagining the author of our nature to be a cunning deceiver

This was not the case in any other matter.

For example, we see that the nature of a triangle has 3 angles are equal to 2 right angles.

But we cannot reach this same conclusion if we were deceived by the author of our nature.

Yet, this supposition on the nature of a triangle assured us of our existence.

Wherever we turn the mind’s eye, we are compelled to conclude that the 3 angles of a triangle are equal to 2 right angles.

This is different from the certainty of our existence. One who does not have the correct idea of a triangle might think that its angles are equal, or not equal, to 2 right angles.

Similarly, a person who does not have the true idea of God might think that he is a deceiver, or not a deceiver.

Therefore we concede that, except for our existence, we cannot be absolutely certain of anything, as long as we do not have the clear and distinct conception of God that makes us affirm that God is supremely truthful, just as our idea of a triangle makes us conclude that its 3 angles are equal to 2 right angles.

This is why we deny the idea that we cannot attain knowledge of anything.

The whole matter hinges on this alone – that we can form such a conception of God as a deceiver or not a deceiver.

• It is not as easy for us to think that God is a deceiver as to think that he is not a deceiver. This compels us to affirm that he is supremely truthful.

When we have formed such an idea, the reason for doubting mathematical truths will be removed.

For in whatever direction we now turn the mind’s eye with the purpose of doubting one of these truths, we shall not find anything that itself does not make us conclude that this truth is most certain, just as was the case with regard to our existence.

For example, if after discovering the idea of God we attend to the nature of a triangle, its idea will compel us to affirm that its three angles are equal to two right angles, whereas if we attend to the idea of God, this too will compel us to affirm that he is supremely truthful, the author and continuous preserver of our nature, and therefore that he is not deceiving us with regard to this truth.

Attending to the idea of God (which we now suppose we have discovered), it will be just as impossible for us to think that he is a deceiver as to think, when attending to the idea of a triangle, that its three angles are not equal to two right angles.

And just as we can form such an idea of a triangle in spite of not knowing whether the author of our nature is deceiving us, so too we can achieve a clear idea of God and set it before us even though also doubting whether the author of our nature is deceiving us in all things. And provided we possess this idea, in whatever way we may have acquired it, it will be enough to remove all doubts, as has just now been shown.

So having made these points, I reply as follows to the difficulty that has been raised. It is not as long as we do not know of God’s existence (for I have not spoken of that) but as long as we do not have a clear and distinct idea of God, that we cannot be certain of anything.

A person might object:

“We cannot be certain of anything until we have a clear and distinct idea of God. But we cannot have a clear and distinct idea of God as long as we do not know whether the author of our nature is deceiving us. Therefore, we cannot be certain of anything as long as we do not know whether the author of our nature is deceiving us, etc.”

I reply by conceding the major premise and denying the minor.

We do have a clear and distinct idea of a triangle, although we do not know whether the author of our nature is deceiving us.

Granted that we have such an idea of God, as I have just shown at some length, we cannot doubt his existence or any mathematical truth.