Whether any god exists is unknown and may be unknowable

Agnosticism affirms that whether any god exists is not known, and may be unknowable. The agnostic neither asserts nor denies the existence of a deity, holding that the available evidence and human reason are insufficient to settle the question. The term was coined by T. H. Huxley in the nineteenth century to name the principle that one should not claim to know what cannot be demonstrated. In its stronger form agnosticism holds the question to be permanently beyond the reach of knowledge; in its weaker form, merely unresolved at present. T. H. Huxley coined the term in 1869, in the context of debates at the Metaphysical Society in London, deliberately setting it against the "gnostics," those early Christian sects and, by extension, any believers claiming certain, revealed knowledge of the divine.

Huxley elaborated the position at length in his 1889 essay simply titled Agnosticism, insisting there that agnosticism "is not a creed but a method," the consistent application to religious questions of the same evidentiary standard science demands elsewhere, so that the label named an epistemic discipline rather than a specific doctrine about what is or is not true. Huxley intended the term partly as a personal declaration of intellectual honesty, remarking that he had simply found a name for a state of mind he had held for as long as he could remember, one that took no comfort in either confident belief or confident denial.

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.