Agnostic atheism or atheistic agnosticism is a philosophical position that encompasses both atheism and agnosticism. Agnostic atheists are atheistic because they do not hold a belief in the existence of any deity, and are agnostic because they claim that the existence of a demiurgic entity or entities is either unknowable in principle or currently unknown in fact.
The agnostic atheist may be contrasted with the agnostic theist, who believes that one or more deities exist but claims that the existence or nonexistence of such is unknown or cannot be known.
One of the earliest definitions of agnostic atheism is that of theologian and philosopher Robert Flint, in his Croall Lecture of 1887–1888 (published in 1903 under the title Agnosticism).
The atheist may however be, and not unfrequently is, an agnostic. There is an agnostic atheism or atheistic agnosticism, and the combination of atheism with agnosticism which may be so named is not an uncommon one.
If a man has failed to find any good reason for believing that there is a God, it is perfectly natural and rational that he should not believe that there is a God; and if so, he is an atheist... if he goes farther, and, after an investigation into the nature and reach of human knowledge, ending in the conclusion that the existence of God is incapable of proof, cease to believe in it on the ground that he cannot know it to be true, he is an agnostic and also an atheist – an agnostic-atheist – an atheist because an agnostic... while, then, it is erroneous to identify agnosticism and atheism, it is equally erroneous so to separate them as if the one were exclusive of the other...
In 1885 Robert G. Ingersoll, popularly known as "The Great Agnostic", explained his comparative view of agnosticism and atheism as follows:
The Agnostic is an Atheist. The Atheist is an Agnostic. The Agnostic says, "I do not know, but I do not believe there is any God." The Atheist says the same.
Epistemological, or agnostic, atheism argues that people cannot know a God or determine the existence of a God.