Agnosticism is distinguished from atheism, which denies that gods exist, and from theism, which affirms one; it is a stance about the limits of knowledge rather than a claim about what is real, and many people combine it with a practical atheism or a residual theism. It rests on the principle, shared with much of the sceptical and scientific tradition, that belief should be proportioned to evidence and that honest inquiry requires admitting ignorance where proof is lacking. The affirmation is presented here as the considered position of those who hold it.
The stance Huxley named had older philosophical roots: ancient Pyrrhonist sceptics, associated with Sextus Empiricus, practised a systematic suspension of judgement (epoche) on questions, including theological ones, that could not be settled by the available evidence, centuries before the modern term existed.
Closer to Huxley's own time, Immanuel Kant, in the Critique of Pure Reason (1781), had argued that the existence of God lies beyond the reach of theoretical reason altogether, neither provable nor disprovable by the tools reason has available, an argument that shaped nineteenth-century religious scepticism well before Huxley gave the position its lasting name.