These two terms are of importance in philosophy. Philosophy is all about using reason alone to explain what is in existence. This means we have to look at our own experience from a subjective position first of all (see the thread about Descartes in the general section) to explain the other things outside of our experience.
a priori
Anything that is a priori is independent of experience, this is anything that we talk about that exists before we experience it. We could say that a priori is objective.
An example of an a priori statement:
All bachelors are unmarried males
To keep things simple, I will leave out the Immanuel Kant usage of this term for another introduction thread. All that matters for now, is that a bachelor will always be an unmarried male by definition and it is therefore independent of my experience, it is before experience and therefore a priori.
a posterori
This kind of knowledge is dependent on experience. So an a posterori statement will look like this:
On this forum, there are unmarried males.
This is not something you could know for sure without checking with members of the forum if they are unmarried or male, that is why it is a posterori.
That’s the basic definitions anyway, I like to think of them as alternative terms for objective and subjective.
Philosophy is not like scientific (as in naturalistic and empirical science that uses the scientific method) knowledge, as it will always start from the mind and will always use language and logic. There are always lots of concepts that simply evade falsification in a scientific method, which doesn’t make philosophy invalid, it just has to come up with new methods and processes to explain what is going on in the world in the best possible way.
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