Starting, then, with these data,--matter, force, and the law of gravitation,--what must happen? We have the strongest scientific reason to believe that the matter of the solar system primordially existed in a highly diffused or nebulous form. By mutual gravitation, therefore, all the substance of the nebula must have begun to concentrate upon itself, or to condense. Now, from this point onwards, I wish it to be clearly understood that the mere consideration of the supposed facts not admitting of scientific proof, or of scientific explanation if true, in no wise affects the certainty of the doctrine which these facts are here adduced to establish. Fully granting that the alleged facts are not beyond dispute, and that, even if true, innumerable other unknown and unknowable facts must have been associated with them--fully admitting, in short, that our ideas concerning the genesis of the solar system are of the crudest and least trustworthy character; still, if it be admitted, what at the present day only ignorance or prejudice can deny, viz., that, as a whole, evolution has been the method of the universe; then it follows that the doctrine here contended for is as certainly true as it would be were we fully acquainted with every cause and every change which has acted and ensued throughout the whole process of the genesis of things. Now, bearing this caveat in mind, we have next to observe that when once the nebula began to condense, new relations among its constituent parts would, _for this reason_, begin to be established. "Given a rare and widely diffused mass of nebulous matter,... what are the successive changes that will take place? Mutual gravitation will approximate its atoms, but their approximation will be opposed by atomic repulsion, the overcoming of which implies the evolution of heat." That is to say, the condensation of the nebula as a whole of necessity implies at least the origination of these new material and dynamical relations among its constituent parts. "As fast as this heat partially escapes by radiation, further approximation will take place, attended by further evolution of heat, and so on continuously: the processes not occurring separately, as here described, but simultaneously, uninterruptedly, and with increasing activity." Hence the newly established relations continuously acquire new increments of intensity. But now observe a more important point. The previous essential conditions remaining unaltered--viz., the persistence of matter and force, as well as, or rather let us say and consequently, the law of gravitation--these conditions, I say, remaining constant, and the newly established relations would necessarily _of themselves_ give origin to _new_ laws. For whenever two given quantities of force and matter met in one of the novel relations, they would of necessity give rise to novel effects; and whenever, on any future occasion, similar quantities of force