Relating to or derived by reasoning from known or observed facts.
The president had come to the a posteriori conclusion that the booming economy was entirely due to his economic policies.
A posteriori is a term for logic. It is Latin for "from the latter." A posteriori usually refers to reasoning that derives causes from effects. This kind of reasoning can sometimes lead to false conclusions. The rising of the sun following the crowing of a rooster, for example, does not mean that the rooster's crowing caused the sun to rise.