Matter, it is true, occupies a somewhat equivocal place in the agnostic philosophy. According to Spencer, it is "built up or extracted from experiences of force," and it is only by force that it "demonstrates itself to us as existing." This is true; but that which "demonstrates itself to us as existing" must exist, in whatever way the demonstration is made, and Spencer does not, in consequence of the lack of direct evidence, extend his Agnosticism to matter, though he might quite consistently do so. In any case, science postulates the existence of matter. Further, science is obliged to conceive of matter as composed of atoms, and of atoms of different kinds; for atoms differ in weight and in chemical properties, and these differences are to us ultimate, for they cannot be changed. Thus science and practical life are tied down to certain predetermined properties of matter. We may, it is true, in future be able to reduce the number of kinds of matter, by finding that some bodies believed to be simple are really compound; but this does not affect the question in hand. As to the origin of the diverse properties of atoms, only two suppositions seem possible: either in some past period they agreed to differ and to divide themselves into different kinds suitable in quantity and properties to make up the universe, or else matter in its various kinds has been skilfully manufactured by a creative power. But there is a scientific way in which matter may be resolved into force. An iron knife passed through a powerful magnetic current is felt to be resisted, as if passing through a solid substance, and this resistance is produced merely by magnetic attraction. Why may it not be so with resistance in general? To give effect to such a supposition, and to reconcile it with the facts of chemistry and of physics, it is necessary to suppose that the atoms of matter are merely minute vortices or whirlwinds set up in an ethereal medium, which in itself, and when at rest, does not possess any of the properties of matter. That such an ethereal medium exists we have reason to believe from the propagation of light and heat through space, though we know little, except negatively, of its properties. Admitting, however, its existence, the setting up in it of the various kinds of vortices constituting the atoms of different kinds of matter is just as much in need of a creative power to initiate it as the creation of matter out of nothing would be. Besides this, we now have to account for the existence of the ether itself; and here we have the disadvantage that this substance possesses none of the properties of ordinary matter except mere extension; that, in so far as we know, it is continuous, and not molecular; and that, while of the most inconceivable tenuity, it transmits vibrations in a manner similar to that of a body of the extremest solidity. It would seem, also, to be indefinite in extent and beyond the control of the ordinary natural forces.