A priori and a posteriori knowledge
The nature of this distinction has been disputed by various philosophers; however, the terms may be roughly defined as follows:
A priori knowledge is knowledge that is known independently of experience (that is, it is non-empirical, or arrived at beforehand, usually by reason). It will henceforth be acquired through anything that is independent from experience.
A posteriori knowledge is knowledge that is known by experience (that is, it is empirical, or arrived at afterward).
A priori knowledge is a way of gaining knowledge without the need of experience. In Bruce Russell’s article “A Priori Justification and Knowledge” he says that it is “knowledge based on a priori justification,” (1) which relies on intuition and the nature of these intuitions. A priori knowledge is often contrasted with posteriori knowledge, which is knowledge gained by experience. A way to look at the difference between the two is through an example. Bruce Russell give two proposition in which the reader decides which one he believes more. Option A: All crows are birds. Option B: All crows are black. If you believe option A, then you are a priori justified in believing it because you don’t have to see a crow to know it’s a bird. If you believe in option B, then you are posteriori justified to believe it because you have seen many crows therefore knowing they are black. He goes on to say that it doesn’t matter if the statement is true or not, only that if you believe in one or the other that matters.
The idea of a priori knowledge is that it is based on intuition or rational insights. Laurence BonJour says in his article “The Structure of Empirical Knowledge”, that a “rational insight is an immediate, non-inferential grasp, apprehension or ‘seeing’ that some proposition is necessarily true.” (3) Going back to the crow example, by Laurence BonJour’s definition the reason you would believe in option A is because you have an immediate knowledge that a crow is a bird, without ever experiencing one.– Acquiring Knowledge
In epistemology, rationalism is the view that “regards reason as the chief source and test of knowledge” or “any view appealing to reason as a source of knowledge or justification”. More formally, rationalism is defined as a methodology or a theory “in which the criterion of the truth is not sensory but intellectual and deductive”. Rationalists believe reality has an intrinsically logical structure. Because of this, rationalists argue that certain truths exist and that the intellect can directly grasp these truths. That is to say, rationalists assert that certain rational principles exist in logic, mathematics, ethics, and metaphysics that are so fundamentally true that denying them causes one to fall into contradiction. Rationalists have such a high confidence in reason that proof and physical evidence are unnecessary to ascertain truth – in other words, “there are significant ways in which our concepts and knowledge are gained independently of sense experience”. Because of this belief, empiricism is one of rationalism’s greatest rivals. –Rationalism
Empiricism is a theory which states that knowledge comes only or primarily from sensory experience. One of several views of epistemology, the study of human knowledge, along with rationalism and skepticism, empiricism emphasizes the role of experience and evidence, especially sensory experience, in the formation of ideas, over the notion of innate ideas or traditions; empiricists may argue however that traditions (or customs) arise due to relations of previous sense experiences.
Empiricism in the philosophy of science emphasizes evidence, especially as discovered in experiments. It is a fundamental part of the scientific method that all hypotheses and theories must be tested against observations of the natural world rather than resting solely on a priori reasoning, intuition, or revelation.
Empiricism, often used by natural scientists, says that “knowledge is based on experience” and that “knowledge is tentative and probabilistic, subject to continued revision and falsification.” One of the epistemological tenets is that sensory experience creates knowledge. The scientific method, including experiments and validated measurement tools, guides empirical research.