process in the vegetation of the downs is seen in the turf, with its weeds and gorse. Under the conditions, they have come out of the struggle victorious; and, by surviving, have proved that they are the fittest to survive.
* That every theory of evolution must be consistent not merely
with progressive development, but with indefinite persistence
in the same condition and with retrogressive modification, is a
point which I have insisted upon repeatedly from the year 1862
till now. See Collected Essays, vol. ii. pp. 461-89; vol. iii.
p. 33; vol. viii. p. 304. In the address on "Geological
Contemporaneity and Persistent Types" (1862), the
paleontological proofs of this proposition were, I believe,
first set forth.
That the state of nature, at any time, is a temporary phase of a process of incessant change, which has been going on for innumerable ages, appears to me to be a proposition as well established as any in modern history.
Paleontology assures us, in addition, that the ancient philosophers who, with less reason, held the same doctrine, erred in supposing that the phases formed a cycle, exactly repeating the past, exactly foreshadowing the future, in their rotations. On the contrary, it furnishes us with conclusive reasons for thinking that, if every link in the ancestry of these humble indigenous plants had been preserved and were accessible to us, the whole would present a converging series of forms of gradually diminishing complexity, until, at some period in the history of the earth, far more remote than any of which organic remains have yet been discovered, they would merge in those low groups among which the Boundaries between animal and vegetable life become effaced.*
* "On the Border Territory between the Animal and the Vegetable
Kingdoms," Essays, vol. viii. p. 162
The word "evolution," now generally applied to the cosmic process, has had a singular history, and is used in various senses.* Taken in its popular signification it means progressive development, that is, gradual change from a condition of relative uniformity to one of relative complexity; but its connotation has been widened to include the phenomena of retrogressive metamorphosis, that is, of progress from a condition of relative complexity to one of relative uniformity.
As a natural process, of the same character as the development of a tree from its seed, or of a fowl from its egg, evolution excludes creation and all other kinds of supernatural intervention. As the expression of a fixed order, every stage of which is the effect of causes operating according to definite rules, the conception of evolution no less excludes that of chance. It is very desirable to remember that evolution is not an explanation of the cosmic process, but merely a generalized statement of the method and results of that process. And, further, that, if there is proof that the cosmic process was set going by any agent, then that agent will be, the creator of it and of all its products, although supernatural intervention may remain strictly excluded from its further course.
So far as that limited revelation of the nature of things, which we call scientific knowledge, has