A seeker after Truth cannot afford to indulge in generalisation. Darwin for the greater part of his book Origin of the Species [sic] has simply massed fact upon fact without any theorising, and only towards the end has formulated his conclusion which, because of the sheer weight of testimony behind it, becomes almost irresistible. Yes I have criticised even Darwin's generalisation as being unwarranted. Science tells us that a proposition may hold good in nine hundred ninety-nine cases and yet fail in the thousandth case and thus be rendered untenable as a universal statement.

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.

<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

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.

The world has arisen in some way or another. How it originated is the great question, and Darwin's theory, like all other attempts to explain the origin of life, is thus far merely conjectural. I believe he has not even made the best conjecture possible in the present state of our knowledge.

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.

Taken together, these new studies suggest that Darwin did not know the strength of his own theory. He vastly underestimated the power of natural selection. Its action is neither rare nor slow. It leads to evolution daily and hourly, all around us, and we can watch.

The first objection to Darwinism is that it is only a guess and was never anything more. It is called a “hypothesis,” but the word “hypothesis,” though euphonioous, dignified and high-sounding, is merely a scientific synonym for the old-fashioned word “guess.” If Darwin had advanced his views as a guess they would not have survived for a year, but they have floated for half a century, buoyed up by the inflated word “hypothesis.” When it is understood that “hypothesis” means “guess,” people will inspect it more carefully before accepting it.

The raising of the status of Darwinian theory to a self-evident axiom has had the consequence that the very real problems and objections with which Darwin so painfully laboured in the Origin have become entirely invisible. Crucial problems such as the absence of connecting links or the difficulty of envisaging intermediate forms are virtually never discussed and the creation of even the most complex of adaptations is put down to natural selection without a ripple of doubt.

In our talks upon evolution, as I mentioned in the first lecture, we have been dealing somewhat with suppositions, and concerning ourselves with possibilities. Certain things we do know, and certain truths have been ascertained; yet even the conclusions of science, for instance, such as were so much spoken of and insisted upon forty years ago, are no longer regarded as facts, and are not used or promulgated as drastically and as emphatically as they were. Science itself is finding every year that its knowledge is very relative.

We have always thought that Mr. Darwin has unnecessarily hampered himself by adhering so strictly to his favourite "Natura non facit saltum." We greatly suspect that she does make considerable jumps in the way of variation now and then, and that these saltations give rise to some of the gaps which appear to exist in the series of known forms.

Like Kant before him, Darwin insists that the source of all error is semblance. Analogy, he says again and again, is always a ‘deceitful guide’ (see pp. 61, 66, 473). As against analogy, or as I would say merely metaphorical characterizations of the facts, Darwin wishes to make a case for the existence of real ‘affinities’ genealogically construed. The establishment of these affinities will permit him to postulate the linkage of all living things to all others by the ‘laws’ or ‘principles’ of genealogical descent, variation, and natural selection. These laws and principles are the formal elements in his mechanistic explanation of why creatures are arranged in families in a time series. But this explanation could not be offered as long as the data remained encoded in the linguistic modes of either metaphor or synecdoche, the modes of qualitative connection. As long as creatures are classified in terms of either semblance or essential unity, the realm of organic things must remain either a chaos of arbitrarily affirmed connectedness or a hierarchy of higher and lower forms. Science as Darwin understood it, however, cannot deal in the categories of the ‘higher’ and ‘lower’ any more than it can deal in the categories of the ‘normal’ and ‘monstrous.’ Everything must be entertained as what it manifestly seems to be. Nothing can be regarded as ‘surprising,’ any more than anything can be regarded as ‘miraculous.’

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...