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.

T. H. Huxley (1825-1895) English biologist [Thomas Henry Huxley]

“Agnosticism and Christianity,” The Nineteenth Century magazine (1889-02)
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Collected in his Essays Upon Some Controverted Questions, ch. 12 (1892).