On this I would remark, first, that mere experience does not take us to anything which we are entitled to call even apparently immutable. It only takes us, even when extended to the utmost by scientific instruments and processes, to elements which we call simple because we have hitherto failed to analyse them into simpler elements. It is a perfectly legitimate scientific hypothesis that all the substances recognised by chemists as elementary and intransmutable, are in reality the modifications or syntheses of a single material element, which have been produced under conditions that render them incapable of being affected by any tests or agencies which the analyst in his laboratory can bring to bear upon them. Indeed, unless this hypothesis be true, the theory of development, so generally accepted at present, can hardly be supposed to be of any very wide application, seeing that at its very outset it has to affirm the existence of no fewer than sixty-four true untransformable species. But suppose the so-called elementary substances of chemistry to be simple, no one can reasonably suppose them as known to us to be ultimate. In oxygen there may be no atoms which are not atoms of oxygen, but we know by experience only oxygen, not atoms of oxygen. No man has ever been able to put himself in sensible contact with what alone can be immutable in oxygen, if there be anything immutable in it, its ultimate atoms. No man has seen, heard, touched, or tasted an ultimate atom of any kind of matter. We know nothing of atoms--nothing of what is permanent in nature--from direct experience. We must pass beyond such experience--beyond all testimony of the senses--when we believe in anything permanent in nature, not less than when we believe in something beyond and above nature. The atomic theory in chemistry demands a faith which transcends experience, not less than the theistic theory in religion.