Quick Definition: Proceeding by inquiry
Agnosticism is the view that the truth values of certain claims—especially claims about the existence or non-existence of God, as well as other religious and metaphysical claims—are unknown or unknowable. According to the philosopher William L. Rowe, in the popular sense, an agnostic is someone who neither believes nor disbelieves in the existence of God, whereas a theist and an atheist believe and disbelieve, respectively.
Thomas Henry Huxley, an English biologist, coined the word agnostic in 1869. However, earlier thinkers have written works that promoted agnostic points of view. These thinkers include Sanjaya Belatthaputta, a 5th-century BCE Indian philosopher who expressed agnosticism about any afterlife,Protagoras, a 5th-century BCE Greek philosopher was agnostic about the gods. The Nasadiya Sukta in the Rigveda is agnostic about the origin of the universe.
Since the time that Huxley coined the term, many other thinkers have extensively written about agnosticism.