We have daily experience of such a state of things in dreams; and I do not suppose that there is anyone, who would maintain that, while he is dreaming, he has the free power of suspending his judgment concerning the things in his dream, and bringing it about that he should not dream those things, which he dreams that he sees; yet it happens, notwithstanding, that even in dreams we suspend our judgment, namely, when we dream that we are dreaming.
Further, I grant that no one can be deceived, so far as actual perception extends--that is, I grant that the mind's imaginations, regarded in themselves, do not involve error (II.
xvii.

note); but I deny, that a man does not, in the act of perception, make any affirmation.

For what is the perception of a winged horse, save affirming that a horse has wings?
If the mind could perceive nothing else but the winged horse, it would regard the same as present to itself: it would have no reasons for doubting its existence, nor any faculty of dissent, unless the imagination of a winged horse be joined to an idea which precludes the existence of the said horse, or unless the mind perceives that the idea which it possess of a winged horse is inadequate, in which case it will either necessarily deny the existence of such a horse, or will necessarily be in doubt on the subject.
I think that I have anticipated my answer to the third objection, namely, that the will is something universal which is predicated of all ideas, and that it only signifies that which is common to all ideas, namely, an affirmation, whose adequate essence must, therefore, in so far as it is thus conceived in the abstract, be in every idea, and be, in this respect alone, the same in all, not in so far as it is considered as constituting the idea's essence: for, in this respect, particular affirmations differ one from the other, as much as do ideas.

For instance, the affirmation which involves the idea of a circle, differs from that which involves the idea of a triangle, as much as the idea of a circle differs from the idea of a triangle.
Further, I absolutely deny, that we are in need of an equal power of thinking, to affirm that that which is true is true, and to affirm that that which is false is true.

These two affirmations, if we regard the mind, are in the same relation to one another as being and not--being; for there is nothing positive in ideas, which constitutes the actual reality of falsehood (II.xxxv.note, and xlvii.