Thus, not only do I exist, but other entities exist also, that is to say, the objects of my sensations; and even if these objects are merely ideas, still these ideas are not me.

But everything outside myself, everything which acts upon my senses, I call matter, and all the particles of matter which I suppose to be united into separate entities I call bodies.  Thus all the disputes of the idealists and the realists have no meaning for me; their distinctions between the appearance and the reality of bodies are wholly fanciful.

I am now as convinced of the existence of the universe as of my own.  I next consider the objects of my sensations, and I find that I have the power of comparing them, so I perceive that I am endowed with an active force of which I was not previously aware.

To perceive is to feel; to compare is to judge; to judge and to feel are not the same.  Through sensation objects present themselves to me separately and singly as they are in nature; by comparing them I rearrange them, I shift them so to speak, I place one upon another to decide whether they are alike or different, or more generally to find out their relations.  To my mind, the distinctive faculty of an active or intelligent being is the power of understanding this word “is.”  I seek in vain in the merely sensitive entity that intelligent force which compares and judges; I can find no trace of it in its nature.  This passive entity will be aware of each object separately, it will even be aware of the whole formed by the two together, but having no power to place them side by side it can never compare them, it can never form a judgment with regard to them.

To see two things at once is not to see their relations nor to judge of their differences; to perceive several objects, one beyond the other, is not to relate them.  I may have at the same moment an idea of a big stick and a little stick without comparing them, without judging that one is less than the other, just as I can see my whole hand without counting my fingers. [Footnote:  M. de le Cordamines’ narratives tell of a people who only know how to count up to three.  Yet the men of this nation, having hands, have often seen their fingers without learning to count up to five.] These comparative ideas, ‘greater’, ‘smaller’, together with number ideas of ‘one’, ‘two’, etc. are certainly not sensations, although my mind only produces them when my sensations occur.

We are told that a sensitive being distinguishes sensations from each other by the inherent differences in the sensations; this requires explanation.  When the sensations are different, the sensitive being distinguishes them by their differences; when they are alike, he distinguishes them because he is aware of them one beyond the other.  Otherwise, how could he distinguish between two equal objects simultaneously experienced?  He would necessarily confound the two objects and take them for one object, especially under a system which professed that the representative sensations of space have no extension.