But this is still more remarkable, when we add a _sympathy_ of parts to their _common end_, and suppose that they bear to each other the reciprocal relation of cause and effect in all their actions and operations. This is the case with all animals and vegetables; where not only the several parts have a reference to some general purpose, but also a mutual dependence on, and connexion with, each other. The effect of so strong a relation is, that though every one must allow, that in a very few years both vegetables and animals endure a _total_ change, yet we still attribute identity to them, while their form, size and substance, are entirely altered. An oak that grows from a small plant to a large tree is still the same oak, though there be not one particle of matter or figure of its parts the same. An infant becomes a man, and is sometimes fat, sometimes lean, without any change in his identity. We may also consider the two following phenomena, which are remarkable in their kind. The first is, that though we commonly be able to distinguish pretty exactly betwixt numerical and specific identity, yet it sometimes happens that we confound them, and in our thinking and reasoning employ the one for the other. Thus, a man who hears a noise that is frequently interrupted and renewed, says it is still the same noise, though 'tis evident the sounds have only a specific identity or resemblance, and there is nothing numerically the same but the cause which produced them. In like manner it may be said, without breach of the propriety of language, that such a church, which was formerly of brick, fell to ruin, and that the parish rebuilt the same church of freestone, and according to modern architecture. Here neither the form nor materials are the same, nor is there any thing common to the two objects but their relation to the inhabitants of the parish; and yet this alone is sufficient to make us denominate them the same. But we must observe, that in these cases the first object is in a manner annihilated before the second comes into existence; by which means, we are never presented, in any one point of time, with the idea of difference and multiplicity; and for that reason are less scrupulous in calling them the same.