The Difference Between Our Sensations and the Things That Produce Them

by Rene Descartes

There is a difference between our sensation of light and the objects that we see.

Words come from human convention. They cause us to conceive of things.

Our ears lets us hear the sound of the words Our eyes lets us see the faces of persons.

But it is our mind that gives us the meaning of those sounds and faces, having remembered what those sounds and that face signify at the same time.[3]

Our mind represents to us the idea of light each time the action that signifies it touches our eye.

Do you think that, even when we do not pay attention to the meaning of words and hear only their sound, the idea of that sound, which forms in our thought, is anything like the object that is the cause of it?

A man opens his mouth, moves his tongue, forces out his breath. = in all these actions I see nothing that is not very different from the idea of the sound that they cause us to imagine.

Sound is a mere vibration of air that strikes against our ears. Thus, if our sense of hearing were to report to our mind the true image of its object, then, instead of causing us to conceive of sound, it would have to cause us to conceive of the motion of the parts of air that then vibrate against our ears.

Of all our senses, touch is the one least misleading and most certain.

Everyone knows the ideas of tickling and of pain. These are formed in our thought when we are touched. This tickling and pain feeling are different from those things touching us.

If you pass a feather over the lips of a child who is falling asleep, and he perceives it, will he [4] conceive it as resembling anything in this feather?

A soldier returns from battle. As he begins to cool off, he feels pain and worries that he has been wounded. He finds that it was nothing but a buckler which was caught under his armor pressing on him. If the image of the buckler appeared to his mind after feeling its pain, then he would not need to worry.

Likewise, the objects that we see is the same as how the touch of a feather causes tickles and the buckler causes pain.