Suppose, however, that the intellectual and vital principle differs in the most marked and essential manner from all other known substances; that they have all some resemblance between themselves which it in no degree participates. In what manner can this concession be made an argument for its imperishability? All that we see or know perishes and is changed. Life and thought differ indeed from everything else. But that it survives that period, beyond which we have no experience of its existence, such distinction and dissimilarity affords no shadow of proof, and nothing but our own desires could have led us to conjecture or imagine. Have we existed before birth? It is difficult to conceive the possibility of this. There is, in the generative principle of each animal and plant, a power which converts the substances by which it is surrounded into a substance homogeneous with itself. That is, the relations between certain elementary particles of matter undergo a change, and submit to new combinations. For when we use the words PRINCIPLE, POWER, CAUSE, we mean to express no real being, but only to class under those terms a certain series of co-existing phenomena; but let it be supposed that this principle is a certain substance which escapes the observation of the chemist and anatomist. It certainly MAY BE; though it is sufficiently unphilosophical to allege the possibility of an opinion as a proof of its truth. Does it see, hear, feel, before its combination with those organs on which sensation depends? Does it reason, imagine, apprehend, without those ideas which sensation alone can communicate? If we have not existed before birth; if, at the period when the parts of our nature on which thought and life depend, seem to be woven together; if there are no reasons to suppose that we have existed before that period at which our existence apparently commences, then there are no grounds for supposition that we shall continue to exist after our existence has apparently ceased. So far as thought is concerned, the same will take place with regard to use, individually considered, after death, as had place before our birth.