The occurrence of successive forms of life upon our globe is an historical fact, which cannot be disputed; and the relation of these successive forms… - Thomas Henry Huxley

It is wrong for a man to say that he is certain of the objective truth of any proposition unless he can produce evidence which logically justifies that certainty.

It is far better for a man to go wrong in freedom than to go right in chains.

Agnosticism is not properly described as a "negative" creed, nor indeed as a creed of any kind, except in so far as it expresses absolute faith in the validity of a principle which is as much ethical as intellectual. This principle may be stated in various ways, but they all amount to this: that it is wrong for a man to say that he is certain of the objective truth of any proposition unless he can produce evidence which logically justifies that certainty. This is what agnosticism asserts; and, in my opinion, it is all that is essential to agnosticism. That which agnostics deny and repudiate as immoral is the contrary doctrine, that there are propositions which men ought to believe, without logically satisfactory evidence; and that reprobation ought to attach to the profession of disbelief in such inadequately supported propositions. The justification of the agnostic principle lies in the success which follows upon its application, whether in the field of natural or in that of civil history; and in the fact that, so far as these topics are concerned, no sane man thinks of denying its validity.