These and the like relations, expressed by relative terms that have others answering them, with a reciprocal intimation, as father and son, bigger and less, cause and effect, are very obvious to every one, and everybody at first sight perceives the relation.  For father and son, husband and wife, and such other correlative terms, seem so nearly to belong one to another, and, through custom, do so readily chime and answer one another in people’s memories, that, upon the naming of either of them, the thoughts are presently carried beyond the thing so named; and nobody overlooks or doubts of a relation, where it is so plainly intimated.  But where languages have failed to give correlative names, there the relation is not always so easily taken notice of.  Concubine is, no doubt, a relative name, as well as wife:  but in languages where this and the like words have not a correlative term, there people are not so apt to take them to be so, as wanting that evident mark of relation which is between correlatives, which seem to explain one another, and not to be able to exist, but together.  Hence it is, that many of those names, which, duly considered, do include evident relations, have been called external denominations.  But all names that are more than empty sounds must signify some idea, which is either in the thing to which the name is applied, and then it is positive, and is looked on as united to and existing in the thing to which the denomination is given; or else it arises from the respect the mind finds in it to something distinct from it, with which it considers it, and then it includes a relation.

3.  Some seemingly absolute Terms contain Relations.

Another sort of relative terms there is, which are not looked on to be either relative, or so much as external denominations:  which yet, under the form and appearance of signifying something absolute in the subject, do conceal a tacit, though less observable, relation.  Such are the seemingly positive terms of old, great, imperfect, &c., whereof I shall have occasion to speak more at large in the following chapters.

4.  Relation different from the Things related.

This further may be observed, That the ideas of relations may be the same in men who have far different ideas of the things that are related, or that are thus compared:  v. g. those who have far different ideas of a man, may yet agree in the notion of a father; which is a notion superinduced to the substance, or man, and refers only to an act of that think called man whereby he contributed to the generation of one of his own kind, let man be what it will.

5.  Change of Relation may be without any Change in the things related.