Other Religions Atheism and Agnosticism God and a Priori vs. a Posteriori: Types of Knowledge Share Flipboard Email Print Logic Sleuth. H. Armstrong Roberts/ClassicStock/Archive Photos/Getty Other Religions Belief Systems Atheism and Agnosticism Logic Ethics Key Figures in Atheism Evolution Atheism Myths and Misconceptions By Austin Cline Atheism Expert M.A., Princeton University B.A., University of Pennsylvania Austin Cline, a former regional director for the Council for Secular Humanism, writes and lectures extensively about atheism and agnosticism. our editorial process Austin Cline Updated February 20, 2018 The phrase a priori is a Latin term which literally means before (the fact). When used in reference to knowledge questions, it means a type of knowledge which is derived without experience or observation. Many consider mathematical truths to be a priori, because they are true regardless of experiment or observation and can be proven true without reference to experimentation or observation. For example, 2 + 2 = 4 is a statement which can be known a priori. When used in reference to arguments, it means an argument which argues solely from general principles and through logical inferences. The term a posteriori literally means after (the fact). When used in reference to knowledge questions, it means a type of knowledge which is derived from experience or observation. Today, the term empirical has generally replaced this. Many empiricists, like Locke and Hume, have argued that all knowledge is essentially a posteriori and that a priori knowledge isn't possible. The distinction between a priori and a posteriori is closely related to the distinctions between analytic/synthetic and necessary/contingent. A Priori Knowledge of God? Some have argued that the very idea of a "god" is an "a priori" concept because most people at least have not had any direct experience of any gods (some claim to have, but those claims cannot be tested). To have developed such a concept in such a way means that there must be something behind the concept and, therefore, God must exist. Against this, atheists will often argue that so-called "a priori concepts" are little more than baseless assertions — and merely asserting that something exists doesn't mean that it does. If one is feeling generous, the concept can be categorized as a fiction. We do, after all, have plenty of concepts of mythical creatures like dragons without actually encountering one. Does that mean that dragons must exist? Of course not. Humans are creative and inventive. Humans have created all sorts of fantastical ideas, concepts, creatures, beings, etc. The mere fact that a human being is capable of imagining something does not justify anyone concluding that that "thing" must also exist out there in the world, independently of human imagination. A Priori Proof of God? Logical and evidential proofs of the existence of gods run into lots of problems. One way that some apologists have attempted to avoid those problems is to construct a proof that doesn't depend on any evidence at all. Known as ontological proofs of God, these arguments purport to demonstrate that some sort of "god" exists based entirely on a priori principles or concepts. Such arguments have a host of their own problems, not the least of which is that they seem to be trying to define "God" into existence. If that were possible, then anything we can imagine would instantly exist simply because we willed it to be so and were capable of using fancy words. That's not a theology that can be taken very seriously, which is probably why it's typically only found in the ivory towers of theologians and ignored by the average believer. A Posteriori Knowledge of God? If it's impossible to establish knowledge of any gods independent of experience, isn't it still possible to do so with experience — to cite people's experiences of a demonstration that a posteriori knowledge of a god is possible? Perhaps, but that would require being able to demonstrate that what the people in question experienced was a god (or was the particular god they claim it to have been). To do so, the people in question would have to be able to demonstrate an ability to distinguish between whatever a "god" is and anything else that might appear to be a god, but isn't. For example, if an investigator claims that a victim of an animal attack was attacked by a dog and not a wolf, they would need to be able to demonstrate that they have the skills and knowledge necessary to distinguish between the two then provide, then provide the evidence they used to reach that conclusion. At least, if you happened to own the dog that was being accused, you'd do that to challenge the conclusion, right? And if they couldn't provide all of that, wouldn't you want your dog to be declared innocent of the attack? That's the most reasonable and rational approach to such a situation, and the claim that someone has experienced some sort of god doesn't deserve anything less, surely.