This, then, is the consideration which we have now to undertake. Relation is to us such a familiar fact that we are apt to forget that it involves all the mystery, if it be a mystery, of the existence of many in one. Whether we say that a related thing is one in itself, manifold in respect of its relations, or that there is one relation between manifold things, e.g., the relation of mutual attraction between bodies—and one expression or the other we must employ in stating the simplest facts—we are equally affirming the unity of the manifold. Abstract the many relations from the one thing, and there is nothing. They, being many, determine or constitute its definite unity. It is not the case that it first exists in its unity, and then is brought into various relations. Without the relations it would not exist at all. In like manner the one relation is a unity of the many things. They, in their manifold being, make the one relation. If these relations really exist, there is a real unity of the manifold, a real multiplicity of that which is one. But a plurality of things cannot of themselves unite in one relation, nor can a single thing of itself bring itself into a multitude of relations. It is true, as we have said, that the single things are nothing except as determined by relations which are the negation of their singleness, but they do not therefore cease to be single things. Their common being is not something into which their several existences disappear. On the contrary, if they did not survive in their singleness, there could be no relation between them—nothing but a blank featureless identity. There must, then, be something other than the manifold things themselves, which combines them without effacing their severalty. (§ 28 ¶ 1)