Smith, George H (1979). Atheism: The Case Against God. стр. 10—11. ISBN9780879751241. „Properly considered, agnosticism is not a third alternative to theism and atheism because it is concerned with a different aspect of religious belief. Theism and atheism refer to the presence or absence of belief in a god; agnosticism refers to the impossibility of knowledge with regard to a god or supernatural being. The term "agnostic" does not, in itself, indicate whether or not one believes in a god. Agnosticism can be either theistic or atheistic.”