She closes by making the point that On the Origin of Species was not so much an original source leading to a dramatic change in worldview for the western world, as it was the result of a change in worldview which had already taken place.
The Origin was the cataclysm that broke up the crust of conventional opinion. It expressed and dramatized what many had obscurely felt. More than this: it legitimized what they felt. Coming from so unexceptional a source, with all the authority of science and without the taint of ulterior ideology, it became the receptacle of great hopes and great fears. Those who were already partial to the mode of thought it represented-which could mean anything from a mild naturalism or deism to a belligerent atheism-often fastened upon it as the symbol and warrant of their belief; if they later loosely spoke of it as the cause of their conversion, the error is understandable, the leap from justification to cause being all too easily effected. Similarly, those who had already committed themselves to the other side, finding naturalism uncongenial or unpersuasive, tended to look upon the Origin as the incarnation of all that was hateful and fearful. There were, to be sure, some who experienced a genuine crisis of faith upon reading it, as there were also some who came to it with an open mind and left unconverted; if the former have been more publicized, it may be because the loss of faith is a more dramatic affair than the retention of faith. For most men, however, the Origin was not an isolated event with isolated consequences. It did not revolutionize their beliefs so much as give public recognition to a revolution that had already occurred. It was belief made manifest, revolution legitimized.