Agnosticism is the philosophical view that certain metaphysical claims–such as the existence of God or the supernatural–are unknown and perhaps unknowable.
According to the philosopher William L. Rowe, "agnosticism is the view that human reason is incapable of providing sufficient rational grounds to justify either the belief that God exists or the belief that God does not exist". Agnosticism is a doctrine or set of rather than a religion as such.
Thomas Henry Huxley, an English biologist, coined the word "agnostic" in 1869. Earlier thinkers, however, had written works that promoted agnostic points of view, such as Sanjaya Belatthaputta, a 5th-century BCE Indian philosopher who expressed agnosticism about any afterlife; and Protagoras, a 5th-century BCE Greek philosopher who expressed agnosticism about "the gods". The Nasadiya Sukta in the Rigveda is agnostic about the origin of the universe.
Agnosticism is of the essence of science, whether ancient or modern. It simply means that a man shall not say he knows or believes that which he has no scientific grounds for professing to know or believe. Consequently, agnosticism puts aside not only the greater part of popular theology, but also the greater part of anti-theology. On the whole, the "bosh" of heterodoxy is more offensive to me than that of orthodoxy, because heterodoxy professes to be guided by reason and science, and orthodoxy does not.
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.
Agnosticism, in fact, is not a creed, but a method, the essence of which lies in the rigorous application of a single principle ... Positively the principle may be expressed: In matters of the intellect, follow your reason as far as it will take you, without regard to any other consideration. And negatively: In matters of the intellect do not pretend that conclusions are certain which are not demonstrated or demonstrable.