And whatsoever laws bind _in foro interno_, may be broken, not only by a fact contrary to the law, but also by a fact according to it, in case a man think it contrary. For though his action in this case, be according to the law; yet his purpose was against the law; which, where the obligation is _in foro interno_, is a breach. [Sidenote: The laws of nature are eternal.] The laws of nature are immutable and eternal; for injustice, ingratitude, arrogance, pride, iniquity, acception of persons, and the rest, can never be made lawful. For it can never be that war shall preserve life, and peace destroy it. [Sidenote: And yet easy.] The same laws, because they oblige only to a desire, and endeavour, I mean an unfeigned and constant endeavour, are easy to be observed. For in that they require nothing but endeavour, he that endeavoureth their performance, fulfilleth them; and he that fulfilleth the law, is just. [Sidenote: The science of these laws, is the true moral philosophy.] And the science of them, is the true and only moral philosophy. For moral philosophy is nothing else but the science of what is _good_, and _evil_, in the conversation, and society of mankind. _Good_, and _evil_, are names that signify our appetites, and aversions; which in different tempers, customs, and doctrines of men, are different: and divers men, differ not only in their judgment, on the senses of what is pleasant, and unpleasant to the taste, smell, hearing, touch, and sight; but also of what is conformable, or disagreeable to reason, in the actions of common life. Nay, the same man, in divers times, differs from himself; and one time praiseth, that is, calleth good, what another time he dispraiseth, and calleth evil: from whence arise disputes, controversies, and at last war. And therefore so long as a man is in the condition of mere nature, which is a condition of war, as private appetite is the measure of good, and evil: and consequently all men agree on this, that peace is good, and therefore also the way, or means of peace, which, as I have shewed before, are _justice_, _gratitude_, _modesty_, _equity_, _mercy_, and the rest of the laws of nature, are good; that is to say; _moral virtues_; and their contrary _vices_, evil. Now the science of virtue and vice, is moral philosophy; and therefore the true doctrine of the laws of nature, is the true moral philosophy. But the writers of moral philosophy, though they acknowledge the same virtues and vices; yet not seeing wherein consisted their goodness; nor that they come to be praised, as the means of peaceable, sociable, and comfortable living, place them in a mediocrity of passions: as if not the cause, but the degree of daring, made fortitude; or not the cause, but the quantity of a gift, made liberality.