To all such extensions we must of course object; there are gaps in the scheme which can be filled in with really great probability, and in such cases there will be no harm done in admitting the probability, while still acknowledging it as such. An overcautious lawyer-like captiousness of spirit in such matters will help no cause and serve no good purpose. Nor is it at all difficult in practice to draw the line and say what is fairly admissible conjecture and what is not. There are other gaps, however, that at present, no real analogy, no fair inferential process, can bridge over; and to all speculations on such subjects, if advanced as more than bare and undisguised guesses, objection must be taken. If this one line had been fairly and firmly adhered to from the first, it can hardly be doubted that much of the acrimony of controversy would have been avoided. It is just as essential at the present moment to insist on the point as ever. But to proceed. Stated in the extreme form, the theory is, that given matter as a beginning, that matter is thenceforth capable, by the aid of fixed and self-working laws, to produce and result in, all the phenomena of life--whether plant, animal, or human--which we see around us. Matter developes from simple to complex forms, growing by its own properties, in directions determined by the circumstances and surroundings of its existence. [Footnote 1: It is enough to instance the theories of Dr. Buchner and, in earlier days, of Oken. The Häckel and Virchow incident in this connection, and the noble protest of the latter against positive teaching of unproved speculation, are in the recollection of all.] If I may put this a little less in the abstract, but more at length, I should describe it thus[1]:-- Astronomers, while watching the course of the stars, have frequently observed in the heavens what they call _nebulae_. With the best telescopes these look like patches of gold-dust or luminous haze in the sky. Some nebulae, it is supposed, really consist of whole systems of stars and suns, but at so enormous a distance that with our best glasses we cannot make more out of them than groups of apparent "star-dust" But other nebulae do not appear to be at this extreme distance, and therefore cannot consist of large bodies. And when their light is examined with the aid of a spectroscope, it gives indications that such nebulae are only masses of vapour, incandescent, or giving out light on account of their being in a burning or highly heated condition. [Footnote 1: The biological evolutionist will, I am aware, object to this, saying that the origin of the cosmos and nebular theories are matters of speculation with which he is not concerned--they are no part of evolution proper. But I submit that the general philosophical evolution does include the whole. At any rate, the materialist view of nature does take in the whole, in such a way as the text indicates.]