Custom and convenience lead us to speak of the "laws" of nature, and of the "powers and forces" of brute matter; and few persons, in adopting these phrases, are aware that they are using a figure of speech. Yet nothing is more certain than that all the researches of science have not been able to point out with certainty a single active cause apart from the operation of mind. We discern nothing but regularity and similarity of sequences; and the attribution of these effects to some occult qualities in the atoms or molecules in which they are manifested is wholly hypothetical, and even, when closely examined, is inconceivable. For this reason we affirm, that the theory of our author, professing to account for the whole work of creation "by the operation of law," is not only unsound and baseless in its particulars, but, when scrutinized as a whole, is absolutely unintelligible. _He attempts to account for a string of hypothetical effects, such as spontaneous generation and the transmutation of species, by a series of hypothetical and inconceivable causes, such as the energies of lifeless matter._ Let any one conceive, if he can, of any _power_, _energy_, or _force_ inherent in a lump of matter,--a stone, for instance,--except this merely negative one, that it always and necessarily remains in its present state, whether this be of rest or motion. Let him point out, if he can, the _nexus_ between what are usually denominated cause and effect in matter,--as when two bodies are drawn towards each other, if they are in opposite states of electricity. When he says that it is the _nature_, or _law_, of bodies thus electrified to attract each other, he offers no explanation of the phenomenon; he only refers it to a class of other results, of a similar character, previously observed. It is not pretended, that all or any of these results, formerly known, are more intelligible or explicable than the one in question. But the latter is classed with them, because, from their general similarity, from their taking place under the same outward circumstances, it is reasonably supposed that _one_ cause, whatever it may be, is common to them all. And this is the whole business of the student of nature, to place together results which are so similar, that we may attribute them to a common cause, without assuming to know what that cause is. The sole office of science is the theory, not of causation, but of classification. It is all reducible to natural history, the essence of which consists in arrangement.