cause, because men are generally ignorant of the causes of their desires. They are, as I have often said already, conscious of their own actions and appetites, but ignorant of the causes whereby they are determined to any particular desire. Therefore, the common saying that Nature sometimes falls short, or blunders, and produces things which are imperfect, I set down among the glosses treated of in the Appendix to Part I. Perfection and imperfection, then, are in reality merely modes of thinking, or notions which we form from a comparison among one another of individuals of the same species; hence I said above (II. Def. vi.), that by reality and perfection I mean the same thing. For we are wont to refer all the individual things in nature to one genus, which is called the highest genus, namely, to the category of Being, whereto absolutely all individuals in nature belong. Thus, in so far as we refer the individuals in nature to this category, and comparing them one with another, find that some possess more of being or reality than others, we, to this extent, say that some are more perfect than others. Again, in so far as we attribute to them anything implying negation—as term, end, infirmity, etc., we, to this extent, call them imperfect, because they do not affect our mind so much as the things which we call perfect, not because they have any intrinsic deficiency, or because Nature has blundered. For nothing lies within the scope of a thing's nature, save that which follows from the necessity of the nature of its efficient cause, and whatsoever follows from the necessity of the nature of its efficient cause necessarily comes to pass.
As for the terms good and bad, they indicate no positive quality in things regarded in themselves, but are merely modes of thinking, or notions which we form from the comparison of things one with another. Thus one and the same thing can be at the same time good, bad, and indifferent. For instance, music is good for him that is