Reasons Which Establish the Existence of God, and the Distinction Between the Mind and Body of Man, Disposed in Geometrical Order
(From the Reply to the Second Objections—Latin, 1670, pp. 85–91. French, Garnier, Tom. II , pp. 74–84)
Definitions
I . By the term “thought” ( cogitatio , pensée ), I comprehend all that is in us, so that we are immediately conscious of it. Thus, all the operations of the will, intellect, imagination, and senses, are thoughts. But I have used the word “immediately” expressly to exclude whatever follows or depends upon our thoughts: for example, voluntary motion has, in truth, thought for its source (principle), but yet it is not itself thought. [Thus walking is not a thought, but the perception or knowledge we have of our walking is.]
II . By the word “idea” I understand that form of any thought, by the immediate perception of which I am conscious of that same thought; so that I can express nothing in words, when I understand what I say, without making it certain, by this alone, that I possess the idea of the thing that is signified by these words. And thus I give the appellation idea not to the images alone that are depicted in the fantasy; on the contrary, I do not here apply this name to them, in so far as they are in the corporeal fantasy, that is to say, in so far as they are depicted in certain parts of the brain, but only in so far as they inform the mind itself, when turned towards that part of the brain.
III . By the objective reality of an idea I understand the entity or being of the thing represented by the idea, in so far as this entity is in the idea;