Secondly, This further may be considered concerning relation, that though it be not contained in the real existence of things, but something extraneous and superinduced, yet the ideas which relative words stand for are often clearer and more distinct than of those substances to which they do belong.  The notion we have of a father or brother is a great deal clearer and more distinct than that we have of a man; or, if you will, paternity is a thing whereof it is easier to have a clear idea, than of humanity; and I can much easier conceive what a friend is, than what God; because the knowledge of one action, or one simple idea, is oftentimes sufficient to give me the notion of a relation; but to the knowing of any substantial being, an accurate collection of sundry ideas is necessary.  A man, if he compares two things together, can hardly be supposed not to know what it is wherein he compares them:  so that when he compares any things together, he cannot but have a very clear idea of that relation.  The ideas, then, of relations, are capable at least of being more perfect and distinct in our minds than those of substances.  Because it is commonly hard to know all the simple ideas which are really in any substance, but for the most part easy enough to know the simple ideas that make up any relation I think on, or have a name for:  v.g. comparing two men in reference to one common parent, it is very easy to frame the ideas of brothers, without having yet the perfect idea of a man.  For significant relative words, as well as others, standing only for ideas; and those being all either simple, or made up of simple ones, it suffices for the knowing the precise idea the relative term stands for, to have a clear conception of that which is the foundation of the relation; which may be done without having a perfect and clear idea of the thing it is attributed to.  Thus, having the notion that one laid the egg out of which the other was hatched, I have a clear idea of the relation of Dam and Chick between the two cassiowaries in St. James’s Park; though perhaps I have but a very obscure and imperfect idea of those birds themselves.

9.  Relations all terminate in simple Ideas.

Thirdly, Though there be a great number of considerations wherein things may be compared one with another, and so a multitude of relations, yet they all terminate in, and are concerned about those simple ideas, either of sensation or reflection, which I think to be the whole materials of all our knowledge.  To clear this, I shall show it in the most considerable relations that we have any notion of; and in some that seem to be the most remote from sense or reflection:  which yet will appear to have their ideas from thence, and leave it past doubt that the notions we have of them are but certain simple ideas, and so originally derived from sense or reflection.