Agnosticism is the view or belief that the existence of God, of the divine or the supernatural is unknown or unknowable. It can be categorized as an indifference or absence of firm beliefs in Theistic religions and Atheism on that basis. Another definition provided 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."

The English biologist Thomas Henry Huxley coined the word agnostic in 1869, and said "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." 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 existence of "the gods".