a priori vs a posteriori

In epistemology, a priori propositions can be known independent of (prior to) experience, whereas a posteriori propositions can be known only on the basis of experience (after experience). Thus, the distinction between a priori and a posteriori corresponds roughly to the distinction between nonempirical and empirical knowledge.

The a priori/a posteriori distinction is applied to ways of knowing, propositions, arguments, and concepts. Because of its dependence upon verification by experience, the foundation for classifying a proposition's as a posteriori is more easily grasped. An a priori concept can be acquired independently of experience, which may include, but is not necessarily confined to innate concepts.

The term 'justification' signifies that the person who believes something has an epistemic reason to thinking that the belief is true. So, to be a priori justified in believing a given proposition is to have a reason independent of experience for thinking that the proposition is true. Such propositions include simple perceptual, numerical, and logical relations – ice water is cooler than boiling water, blue is a colour, three plus two is five, when comparing two men the taller man is not shorter than the shorter man. One is a priori justified in believing a given proposition if, on the basis of pure thought or reason, one has a reason to consider the proposition to be true.

Quo Vadis?
...section index...

Logic

Logic can be symbolic or informal.

Symbolic logic examines the precise symbolic representation of logical concepts, the abstract relationships between these concepts, and the systematization of these relationships. Informal logic involves the application of logical principles to assessment the types of informal arguments and claims that we encounter in daily life.

Propositional logic is a branch of symbolic logic dealing with propositions as units and with their combinations and the connectives that relate them – if, then compound statements. Propositional Logic Terms and Symbols Proposition evaluator.

Categorical logic and categorical syllogisms are more concrete than is propositional logic – some, all, and/not. Venn diagram evaluator.

An understanding of Fallacies of Logic – recognized structural errors in argumentation – provides a shortcut to assessing the cogency of an argument. We most often encounter propositional arguments in daily life, while the logic of science, and of mathematics in particular, is more often categorical.

Quo Vadis?
...section index...