Teizem je v splošnem opredeljen kot vera v obstoj in vsaj enega božanstva in njegovo vplivanje na svet.[1] V običajnem jeziku ali v nasprotju z deizmom izraz pogosto opisuje klasično pojmovanje boga, ki ga najdemo v monoteizmu (imenovanem tudi klasični teizem) ali pojmovanja bogov v politeističnih religijah – vero v boga ali v bogove brez zavračanja razodetja, kot je značilno za deizem.[2][3] Gnosticizem je vera v osebno duhovno znanje.
Ateizem se običajno razume kot nesprejemanje ali zavračanje teizma v najširšem pomenu teizma, tj. nesprejemanje ali zavračanje vere v boga ali bogove.[4][5] Povezana, vendar ločena, je trditev, da je obstoj katerega koli božanstva neznan ali nespoznaven: agnosticizem.[6][7] V kombinaciji s teizmom je nastal agnostični teizem.
Nielsen, Kai (2010). »Atheism«. Encyclopædia Britannica. Pridobljeno 26. januarja 2011. Atheism, in general, the critique and denial of metaphysical beliefs in God or spiritual beings.... Instead of saying that an atheist is someone who believes that it is false or probably false that there is a God, a more adequate characterization of atheism consists in the more complex claim that to be an atheist is to be someone who rejects belief in God for the following reasons (which reason is stressed depends on how God is being conceived)...
Edwards, Paul (2005) [1967]. »Atheism«. V Donald M. Borchert (ur.). The Encyclopedia of Philosophy. Zv. 1 (2. izd.). MacMillan Reference USA (Gale). str. 359. ISBN 9780028657806. On our definition, an 'atheist' is a person who rejects belief in God, regardless of whether or not his reason for the rejection is the claim that 'God exists' expresses a false proposition. People frequently adopt an attitude of rejection toward a position for reasons other than that it is a false proposition. It is common among contemporary philosophers, and indeed it was not uncommon in earlier centuries, to reject positions on the ground that they are meaningless. Sometimes, too, a theory is rejected on such grounds as that it is sterile or redundant or capricious, and there are many other considerations which in certain contexts are generally agreed to constitute good grounds for rejecting an assertion.
(page 175 in 1967 edition)
Hepburn, Ronald W. (2005) [1967]. »Agnosticism«. V Donald M. Borchert (ur.). The Encyclopedia of Philosophy. Zv. 1 (2. izd.). MacMillan Reference USA (Gale). str. 92. ISBN 9780028657806. In the most general use of the term, agnosticism is the view that we do not know whether there is a God or not.
(page 56 in 1967 edition)
Rowe, William L. (1998). »Agnosticism«. V Edward Craig (ur.). Routledge Encyclopedia of Philosophy. Taylor & Francis. ISBN 978-0-415-07310-3. In the popular sense, an agnostic is someone who neither believes nor disbelieves in God, whereas an atheist disbelieves in God. In the strict sense, however, 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. In so far as one holds that our beliefs are rational only if they are sufficiently supported by human reason, the person who accepts the philosophical position of agnosticism will hold that neither the belief that God exists nor the belief that God does not exist is rational.