It would make a volume to go over all sorts of relations: it is not, therefore, to be expected that I should here mention them all. It suffices to our present purpose to show by these, what the ideas are we have of this comprehensive consideration called relation. Which is so various, and the occasions of it so many, (as many as there can be of comparing things one to another,) that it is not very easy to reduce it to rules, or under just heads. Those I have mentioned, I think, are some of the most considerable; and such as may serve to let us see from whence we get our ideas of relations, and wherein they are founded. But before I quit this argument, from what has been said give me leave to observe:
18. All relations terminate in simple ideas. First, That it is evident, that all relation terminates in, and is ultimately founded on, those simple ideas we have got from sensation or reflection: so that all we have in our thoughts ourselves, (if we think of anything, or have any meaning), or would signify to others, when we use words standing for relations, is nothing but some simple ideas, or collections of simple ideas, compared one with another. This is so manifest in that sort called proportional, that nothing can be more.
For when a man says "honey is sweeter than wax," it is plain that his thoughts in this relation terminate in this simple idea, sweetness; which is equally true of all the rest: though, where they are compounded, or decompounded, the simple ideas they are made up of, are, perhaps, seldom taken notice of: v.g. when the word father is mentioned: first, there is meant that particular species, or collective idea, signified by the word man; secondly, those sensible simple ideas, signified by the word generation; and, thirdly, the effects of it, and all the simple ideas signified by the word child.
So the word friend, being taken for a man who loves and is ready to do good to another, has all these following ideas to the making of it up:
first, all the simple ideas, comprehended in the word man, or intelligent being; secondly, the idea of love; thirdly, the idea of readiness or disposition; fourthly, the idea of action, which is any kind of thought or motion; fifthly, the idea of good, which signifies anything that may advance his happiness, and terminates at last, if examined, in particular simple ideas, of which the word good in general signifies any one: but, if removed from all simple ideas quite, it signifies nothing at all. And thus also all moral words terminate at last, though perhaps more remotely, in a collection of simple ideas: the immediate signification of relative words, being very often other supposed known relations; which, if traced one to another, still end in simple ideas.
19. We have ordinarily as clear a notion of the relation, as of the simple ideas in things on which it is founded. Secondly, That in relations, we have for the most part, if not always, as clear a notion of the relation as we have of those simple ideas wherein it is founded: agreement or disagreement, whereon relation depends, being things whereof we have commonly as clear ideas as of any other whatsoever; it being but the distinguishing simple ideas, or their degrees one from another, without which we could have no distinct knowledge at all. For, if I have a clear idea of sweetness, light, or extension, I have, too, of equal, or more, or less, of each of these: if I know what it is for one man to be born of a woman, viz.
Sempronia, I know what it is for another man to be born of the same woman Sempronia; and so have as clear a notion of brothers as of births, and perhaps clearer. For if I believed that Sempronia digged Titus out of the parsley-bed, (as they used to tell children), and thereby became his mother; and that afterwards, in the same manner, she digged Caius out of the parsley-bed, I had as clear a notion of the relation of brothers between them, as if I had all the skill of a midwife: the notion that the same woman contributed, as mother, equally to their births, (though I were ignorant or mistaken in the manner of it), being that on which I grounded the relation; and that they agreed in that circumstance of birth, let it be what it will. The comparing them then in their descent from the same person, without knowing the particular circumstances of that descent, is enough to found my notion of their having, or not having the relation of brothers. But though the ideas of particular relations are capable of being as clear and distinct in the minds of those who will duly consider them as those of mixed modes, and more determinate than those of substances: yet the names belonging to relation are often of as doubtful and uncertain signification as those of substances or mixed modes; and much more than those of simple ideas. Because relative words, being the marks of this comparison, which is made only by men's thoughts, and is an idea only in men's minds, men frequently apply them to different comparisons of things, according to their own imaginations; which do not always correspond with those of others using the same name.
20. The notion of relation is the same, whether the rule any action is compared to be true or false. Thirdly, That in these Icall moral relations, I have a true notion of relation, by comparing the action with the rule, whether the rule be true or false. For if I measure anything by a yard, I know whether the thing I measure be longer or shorter than that supposed yard, though perhaps the yard Imeasure by be not exactly the standard: which indeed is another inquiry. For though the rule be erroneous, and I mistaken in it; yet the agreement or disagreement observable in that which I compare with, makes me perceive the relation. Though, measuring by a wrong rule, Ishall thereby be brought to judge amiss of its moral rectitude;because I have tried it by that which is not the true rule: yet I am not mistaken in the relation which that action bears to that rule Icompare it to, which is agreement or disagreement.
Chapter XXIX