For the rest, M. Liebig confesses that it is IMPOSSIBLE FOR THE MIND to conceive of particles absolutely indivisible; he recognizes, further, that the FACT of this indivisibility is not proved; but he adds that science cannot dispense with this hypothesis: so that, by the confession of its teachers, chemistry has for its point of departure a fiction as repugnant to the mind as it is foreign to experience. What irony! Atoms are unequal in weight, says M. Liebig, because unequal in volume: nevertheless, it is impossible to demonstrate that chemical equivalents express the relative weight of atoms, or, in other words, that what the calculation of atomic equivalents leads us to regard as an atom is not composed of several atoms. This is tantamount to saying that MORE MATTER weighs more than LESS MATTER; and, since weight is the essence of materiality, we may logically conclude that, weight being universally identical with itself, there is also an identity in matter; that the differences of simple bodies are due solely, either to different methods of atomic association, or to different degrees of molecular condensation, and that, in reality, atoms are transmutable: which M. Liebig does not admit. "We have," he says, "no reason for believing that one element is convertible into another element" (p. 135). What do you know about it? The reasons for believing in such a conversion can very well exist and at the same time escape your attention; and it is not certain that your intelligence in this respect has risen to the level of your experience. But, admitting the negative argument of M. Liebig, what follows? That, with about fifty-six exceptions, irreducible as yet, all matter is in a condition of perpetual metamorphosis. Now, it is a law of our reason to suppose in Nature unity of substance as well as unity of force and system; moreover, the series of chemical compounds and simple substances themselves leads us irresistibly to this conclusion. Why, then, refuse to follow to the end the road opened by science, and to admit an hypothesis which is the inevitable result of experience itself? M. Liebig not only denies the transmutability of elements, but rejects the spontaneous formation of germs. Now, if we reject the spontaneous formation of germs, we are forced to admit their eternity; and as, on the other hand, geology proves that the globe has not been inhabited always, we must admit also that, at a given moment, the eternal germs of animals and plants were born, without father or mother, over the whole face of the earth. Thus, the denial of spontaneous generation leads back to the hypothesis of spontaneity: what is there in much-derided metaphysics more contradictory?