In the state of nature, therefore, sin is inconceivable; it can only exist in a state, where good and evil are pronounced on by common consent, and where everyone is bound to obey the State authority. Sin, then, is nothing else but disobedience, which is therefore punished by the right of the State only. Obedience, on the other hand, is set down as merit, inasmuch as a man is thought worthy of merit, if he takes delight in the advantages which a State provides.
Again, in the state of nature, no one is by common consent master of anything, nor is there anything in nature, which can be said to belong to one man rather than another: all things are common to all. Hence, in the state of nature, we can conceive no wish to render to every man his own, or to deprive a man of that which belongs to him; in other words, there is nothing in the state of nature answering to justice and injustice. Such ideas are only possible in a social state, when it is decreed by common consent what belongs to one man and what to another.
From all these considerations it is evident, that justice and injustice, sin and merit, are extrinsic ideas, and not attributes which display the nature of the mind. But I have said enough.
Prop. XXXVIII. Whatsoever disposes the human body, so as to render it capable of being affected in an increased number of ways, or of affecting external bodies in an increased number of ways, is useful to man; and is so, in proportion as the body is thereby rendered more capable of being affected or affecting other bodies in an increased number of ways; contrariwise, whatsoever renders the body less capable in this respect is hurtful to man.
Proof.- Whatsoever thus increases the capabilities of the body increases also the mind's capability of perception (II:xiv.); therefore, whatsoever thus disposes the body and thus renders it capable, is necessarily good or useful (IV:xxvi., IV:xxvii.); and is so in proportion to the extent to which it can render the body capable; contrariwise (II:xiv., IV:xxvi., IV:xxvii.), it is hurtful, if it renders the body in this respect less capable. Q.E.D.
Prop. XXXIX. Whatsoever brings about the preservation of the proportion of motion and rest, which the parts of the human body mutually possess, is good; contrariwise, whatsoever causes a change in such proportion is bad.
Proof.- The human body needs many other bodies for its preservation (II:Post.iv.). But that which constitutes the specific reality (forma) of a human body is, that its parts communicate their several motions one to another in a certain fixed proportion (Def. before Lemma iv. after II:xiii.). Therefore, whatsoever brings about the preservation of the proportion between motion and rest, which the parts of the human body mutually possess, preserves the specific reality of the human body, and consequently renders the human body capable of being affected in many ways and of affecting external bodies in many ways; consequently it is good (by the last Prop.). Again, whatsoever brings about a change in the aforesaid proportion causes the human body to assume another specific character, in other words (see Preface to this Part towards the end, though the point is indeed self-evident), to be destroyed, and consequently totally incapable of being affected in an increased numbers of ways; therefore it is bad. Q.E.D.
Note.- The extent to which such causes can injure or be of service to the mind will be explained in the Fifth Part. But I would here remark that I consider that a body undergoes death, when the proportion of motion and rest which obtained mutually among its several parts is changed. For I do not venture to deny that a human body, while keeping the circulation of the blood and other properties, wherein the life of a body is thought to consist, may none the less be changed into another nature totally different from its own. There is no reason, which compels me to maintain that a body does not die, unless it becomes a corpse; nay, experience would seem to point to the opposite conclusion. It sometimes happens, that a man undergoes such changes, that I should hardly call him the same. As I have heard tell of a certain Spanish poet, who had been seized with sickness, and though he recovered therefrom yet remained so oblivious of his past life, that he would not believe the plays and tragedies he had written to be his own: indeed, he might have been taken for a grown-up child, if he had also forgotten his native tongue. If this instance seems incredible, what shall we say of infants? A man of ripe age deems their nature so unlike his own, that he can only be persuaded that he too has been an infant by the analogy of other men. However, I prefer to leave such questions undiscussed, lest I should give ground to the superstitious for raising new issues.
Prop. XL. Whatsoever conduces to man's social life, or causes men to live together in harmony, is useful, whereas whatsoever brings discord into a State is bad.
Proof.- For whatsoever causes men to live together in harmony also causes them to live according to reason (IV:xxxv.), and is therefore (IV:xxvi. and IV:xxvii.) good, and (for the same reason) whatsoever brings about discord is bad. Q.E.D.
Prop. XLI. Pleasure in itself is not bad but good: contrariwise, pain in itself is bad.
Proof.- Pleasure (III:xi.&Note) is emotion, whereby the body's power of activity is increased or helped; pain is emotion, whereby the body's power of activity is diminished or checked; therefore (IV:xxxviii.) pleasure in itself is good, &c. Q.E.D.
Prop. XLII. Mirth cannot be excessive, but is always good; contrariwise, Melancholy is always bad.
