Benedictus de Spinoza 
Ethics — Part 4 [EPUB ebook] 

PART IV: Of Human Bondage, or the Strength of the Emotions
PREFACE
Human infirmity in moderating and checking the emotions I name bondage: for, when a man is a prey to his emotions, he is not his own master, but lies at the mercy of fortune: so much so, that he is often compelled, while seeing that which is better for him, to follow that which is worse. Why this is so, and what is good or evil in the emotions, I propose to show in this part of my treatise. But, before I begin, it would be well to make a few prefatory observations on perfection and imperfection, good and evil.
When a man has purposed to make a given thing, and has brought it to perfection, his work will be pronounced perfect, not only by himself, but by everyone who rightly knows, or thinks that he knows, the intention and aim of its author. For instance, suppose anyone sees a work (which I assume to be not yet completed), and knows that the aim of the author of that work is to build a house, he will call the work imperfect; he will, on the other hand, call it perfect, as soon as he sees that it is carried through to the end, which its author had purposed for it. But if a man sees a work, the like whereof he has never seen before, and if he knows not the intention of the artificer, he plainly cannot know, whether that work be perfect or imperfect. Such seems to be the primary meaning of these terms.