To this day, and in quarters where they should know better, Darwinism is widely regarded as a theory of ‘chance’.
It is grindingly, creakingly, crashingly obvious that, if Darwinism were really a theory of chance, it couldn’t work. You don’t need to be a mathematician or physicist to calculate that an eye or a haemoglobin molecule would take from here to infinity to self-assemble by sheer higgledy-piggledy luck. Far from being a difficulty peculiar to Darwinism, the astronomic improbability of eyes and knees, enzymes and elbow joints and the other living wonders is precisely the problem that any theory of life must solve, and that Darwinism uniquely does solve.

Although Darwin was an innovator, his ideas rested on a foundation of fact and analysis that naturalists and explorers around the world had built up over the course of a century or more.

Darwinism is not a theory of random chance. It is a theory of random mutation plus non-random cumulative natural selection. . . . Natural selection . . . is a non-random force, pushing towards improvement. . . . Every generation has its Darwinian failures but every individual is descended only from previous generations' successful minorities. . . . [T]here can be no going downhill - species can't get worse as a prelude to getting better. . . . There may be more than one peak.

Darwin had found a way in which a species could be shaped to fit its environment—not by divine intervention, not by mind, but through the steady, relentless working of natural law. Just like the Huttonian prescription for the Earth, it was a Newtonian scheme for life. For better or worse, Darwin transformed our view of our place in the universe. Humans too are not the outcome of a divine design, but simply products of the relentless workings of natural laws, just like rivers and mountains, beetles and whales.

I adopt Mr. Darwin's hypothesis, therefore, subject to the production of proof that physiological species may be produced by selective breeding; just as a physical philosopher may accept the undulatory theory of light, subject to the proof of the existence of the hypothetical ether; or as the chemist adopts the atomic theory, subject to the proof of the existence of atoms; and for exactly the same reasons, namely, that it has an immense amount of primâ facie probability: that it is the only means at present within reach of reducing the chaos of observed facts to order; and lastly, that it is the most powerful instrument of investigation which has been presented to naturalists since the invention of the natural system of classification and the commencement of the systematic study of embryology.

There can be no question that Darwin had nothing like sufficient evidence to establish his theory of evolution. . . . His general theory, that all life on earth had originated and evolved by a gradual successive accumulation of fortuitous mutations, is still, as it was in Darwin’s time, a highly speculative hypothesis entirely without direct factual support and very far from that self-evident axiom some of its more aggressive advocates would have us believe. . . . One might have expected that a theory of such cardinal importance, a theory that literally changed the world, would have been something more than metaphysics, something more than a myth.

One of the most important presuppositions of Darwin's entire thesis is gradualism, the idea that mutations to the genome can cause minor variations in the organism's properties, which can be accumulated piecemeal, bit by bit, over the eons to create the complex order found in the organisms we observe.

When Charles Darwin created the philosophy of natural history (for no less title is due to the idea which transformed the knowledge of organic nature from a multitude of particulars into a continuous whole), he was working in the same spirit and towards the same ends as the great publicists who, heeding his field of labour as little as he heeded theirs, had laid in the patient study of historical fact the bases of a solid and rational philosophy of politics and law. Savigny, whom we do not yet know or honour enough, and our own Burke, whom we know and honour, but cannot honour too much, were Darwinians before Darwin. In some measure the same may be said of the great Frenchman Montesquieu, whose unequal but illuminating genius was lost in a generation of formalists.

Physiologic facts concerning the origin of species in nature were unknown in the time of Darwin. . . The experience of the breeders was quite inadequate to the use which Darwin made of it. It was neither scientific, nor critically accurate. Laws of variation were barely conjectured; the different types of variability were only imperfectly distinguished. The breeders' conception was fairly sufficient for practical purposes, but science needed a clear understanding of the factors in the general process of variation. Repeatedly Darwin tried to formulate these causes, but the evidence available did not meet his requirements. Quetelet's law of variation had not yet been published. Mendel's claim of hereditary units for the explanation of certain laws of hybrids discovered by him, was not yet made. The clear distinction between spontaneous and sudden changes, as compared with the ever-present fluctuating variations, is only of late coming into recognition by agriculturists. Innumerable minor points which go to elucidate the breeders' experience, and with which we are now quite familiar, were unknown in Darwin's time. No wonder that he made mistakes, and laid stress on modes of descent, which have since been proved to be of minor importance or even of doubtful validity.

Darwin and his intellectual descendants have provided us with fundamental insight into the nature of the world we live in and of our place within it, a contribution to our basic metaphysics. It is still widely supposed that this is the sort of thing that should come from philosophers or even theologians. In this case, at any rate, the insight has come from biology and I, as a philosopher, am happy just to do my best to interpret it. The theologians, I have suggested, can be less complacent about this insight, and may even need to retrain for a discipline with a subject matter with stronger claims to existence.

Mr. Darwin's hypothesis is not, so far as I am aware, inconsistent with any known biological fact; on the contrary, if admitted, the facts of Development, of Comparative Anatomy, of Geographical Distribution, and of Palaeontology, become connected together, and exhibit a meaning such as they never possessed before; and I, for one, am fully convinced that if not precisely true, that hypothesis is as near an approximation to the truth as, for example, the Copernican hypothesis was to the true theory of the planetary motions.

In Darwin’s version of Darwinism, natural selection played a key role, but so too did various living agencies, notably one that Darwin called “use and disuse” (using or failing to use a limb or organ, which, he assumed, would have heritable effects) and another that he named “sexual selection.”

<nowiki>[</nowiki>Darwin’s] inquiry characteristically confines itself to the process of cumulative change. His results, as well as his specific determination of the factors at work in this process of cumulative change, have been questioned; perhaps they are open to all the criticisms levelled against them as well as a few more not thought of; but the scope and method given to scientific enquiry by Darwin and the generation whose spokesman he is has substantially not been questioned, except by that diminishing contingent of the faithful

In Darwin's theory, you just have to substitute 'mutations' for his 'slight accidental variations' (just as quantum theory substitutes 'quantum jump' for 'continuous transfer of energy'). In all other respects little change was necessary in Darwin's theory...