[52] (1) Every perception has for its object either a thing considered as existing, or solely the essence of a thing. (2) Now "fiction" is chiefly occupied with things considered as existing. (3) I will, therefore, consider these first--I mean cases where only the existence of an object is feigned, and the thing thus feigned is understood, or assumed to be understood. (4) For instance, I feign that Peter, whom I know to have gone home, is gone to see me, [r] or something of that kind. (5) With what is such an idea concerned? (6) It is concerned with things possible, and not with things necessary or impossible. [53] (1) I call a thing impossible when its existence would imply a contradiction; necessary, when its non-existence would imply a contradiction; possible, when neither its existence nor its non-existence imply a contradiction, but when the necessity or impossibility of its nature depends on causes unknown to us, while we feign that it exists. (2) If the necessity or impossibility of its existence depending on external causes were known to us, we could not form any fictitious hypotheses about it; [54] (1) Whence it follows that if there be a God, or omniscient Being, such an one cannot form fictitious hypotheses. (2) For, as regards ourselves, when I know that I exist, [s] I cannot hypothesize that I exist or do not exist, any more than I can hypothesize an elephant that can go through the eye of a needle; nor when I know the nature of God, can I hypothesize that He or does not exist. [t] (54:3) The same thing must be said of the Chimaera, whereof the nature implies a contradiction. (4) From these considerations, it is plain, as I have already stated, that fiction cannot be concerned with eternal truths. [u] [55] (1) But before proceeding further, I must remark, in passing, that the difference between the essence of one thing and the essence of another thing is the same as that which exists between the reality or existence of one thing and the reality or existence of another; therefore, if we wished to conceive the existence, for example, of Adam, simply by means of existence in general, it would be the same as if, in order to conceive his existence, we went back to the nature of being, so as to define Adam as a being. (2) Thus, the more existence is conceived generally, the more is it conceived confusedly and the more easily can it be ascribed to a given object. (55:3) Contrariwise, the more it is conceived particularly, the more is it understood clearly, and the less liable is it to be ascribed, through negligence of Nature's order, to anything save its proper object. (4) This is worthy of remark.