The apology offered in the Preface to the first volume of this series for the occurrence of repetitions, is even more needful here I am afraid. But it could hardly be otherwise with speeches and essays, on the same topic, addressed at intervals, during more than thirty years, to widely distant and different hearers and readers. The oldest piece, that “On the Educational Value of the Natural History Sciences,” contains some crudities, which I repudiated when the lecture was first reprinted, more than twenty years ago; but it will be seen that much of what I have had to say, later on in life, is merely a development of the propositions enunciated in this early and sadly-imperfect piece of work.

Huxley used the term 'agnostic' to describe his own views on religion, a term whose use has continued to the present day, and which throws light on his demanding criteria for proof in science.

Thomas Henry Huxley (4 May 1825 – 29 June 1895) was an English biologist (comparative anatomist), known as "Darwin's Bulldog" for his advocacy of Charles Darwin's theory of evolution.