It is the negation of that view which deems external forces alone sufficient, and at the same time the assertion of something positive, to be arrived at by the process of _reductio ad absurdum_.
All physical explanations result ultimately in such conceptions of innate power, or else in that of will force.

The far-famed explanation of the celestial motions ends in the conception that every particle of matter has the innate power of attracting every other particle directly as the mass, and inversely as the square of the distance.
We are logically driven to this positive conception if we do not accept the view that there is no force but volition, and that all phenomena whatever are the immediate results of the action of intelligent and self-conscious will.
We have seen that the notion of sudden changes--saltatory actions in nature--has received countenance from Professor Huxley.[233] We must conceive that these jumps are orderly, and according to law, inasmuch as the whole cosmos is such.

Such orderly evolution harmonizes with a teleology derived, not indeed from external nature directly, but from the mind of man.

On this point, however, more will be said in the next chapter.
But, once more, if new species are not manifested by the action of external conditions upon minute indefinite individual differences, in what precise way may we conceive that manifestation to have taken place?
Are new species now evolving, as they have been from time to time evolved?
If so, in what way and by what conceivable means?
{232} In the first place, they must be produced by natural action in pre-existing material, or by supernatural action.
For reasons to be given in the next chapter, the second hypothesis need not be considered.
If, then, new species are and have been evolved from pre-existing material, must that material have been organic or inorganic?
As before said, additional arguments have lately been brought forward to show that individual organisms _do_ arise from a basis of _in_-organic material only.

As, however, this at the most appears to be the case, if at all, only with the lowest and most minute organisms exclusively, the process cannot be observed, though it may perhaps be fairly inferred.
We may therefore, if for no other reason, dismiss the notion that highly organized animals and plants can be suddenly or gradually built up by any combination of physical forces and natural powers acting externally and internally upon and in merely inorganic material as a base.
But the question is, how have the highest kinds of animals and plants arisen?
It seems impossible that they can have appeared otherwise than by the agency of antecedent organisms not greatly different from them.
A multitude of facts, ever increasing in number and importance, all point to such a mode of specific manifestation.
One very good example has been adduced by Professor Flower in the introductory lecture of his first Hunterian Course.[234] It is the reduction in size, to a greater or less degree, of the second and third digits of the foot in Australian marsupials, and this, in spite of the very different form and function of the foot in different groups of those animals.
A similarly significant evidence of relationship is afforded by processes of the zygomatic region of the skull in certain edentates existing and extinct.
{233} Again, the relation between existing and recent faunas of the different regions of the world, and the predominating (though by no means exclusive) march of organization, from the more general to the more special, point in the same direction.
Almost all the facts brought forward by the patient industry of Mr.Darwin in support of his theory of "Natural Selection," are of course available as evidence in favour of the agency of pre-existing and similar animals in specific evolution.
Now the new forms must be produced by changes taking place in organisms in, after or before their birth, either in their embryonic, or towards or in their adult, condition.
Examples of strange births are sufficiently common, and they may arise either from direct embryonic modifications or apparently from some obscure change in the parental action.