People approach epistemology in various ways; the following categories originally reflected divisions among schools of philosophy in the seventeenth and eighteenth centuries, but may prove useful in categorizing certain approximate trends throughout the history of epistemology:
- (1) Rationalists believe there are innate ideas that are not found in experience. These ideas exist independently of any experience people may have. These ideas may in some way derive from the structure of the human mind, or they may exist independently of the mind. If they exist independently, they may be understood by a human mind once it reaches a necessary degree of sophistication.
- (2) Empiricists (see: scientific method, philosophy of science naive empiricism) deny that there are concepts that exist prior to experience. For them, all knowledge is a product of human learning, based on human perception. Perception, however, may cause concern, since illusions, misunderstandings, and hallucinations prove that perception does not always depict the world as it really is.
- Some say the existence of mathematical theorems poses a problem for empiricists. Mathematical truths certainly do not depend on experience, and they can be known prior to experience. Some empiricists reply that all mathematical theorems are empty of cognitive content, as they only express the relationship of concepts to one another. Rationalists would hold that such relationships are indeed a form of cognitive content.
- (3) The German philosopher Immanuel Kant is widely understood as having worked out a synthesis between these views. In Kant's view people certainly do have knowledge that is prior to experience, which is not devoid of cognitive significance. For example, the principle of causality. He held that there are a priori synthetic concepts.
No consensus exists as to which epistemology will prove the most productive in allowing human beings to have the most accurate understanding of the world. All people use an epistemology, even if unconsciously. Thinking beings cannot understand and analyze ideas without first having a system to accept and analyze information in the first place, which we all do. All people - even children - possess rudimentary and undeveloped epistemologies. However, those who study some philosophy and logic can begin to recognize how their own epistemologies work, and such people can choose to change their epistemology.
An analysis of this topic would be dependent on the system one used to begin with. One might wonder: What do I have to do, to be sure that I do have the truth? How can I be sure that my beliefs are true? Is there some sort of guarantee available to me -- some sort of criterion I might use, in order to decide, as rationally and as carefully as I possibly could, that indeed what I believe is actually true?
Suppose someone thought that his or her belief had been arrived at rationally. Using logic, one might base his or her belief on observation and experiment, conscientiously answer objections, and so forth. Accordingly, one would conclude that his or belief is rational. If so, then one's belief has at least some claim to be true. Rationality provides an indicator of truth: if your belief is rational, then it is at least probably true. At the very least, the rationality of a belief gives reason to think the belief is true.
There are a number of features of beliefs, such as rationality, justification, and probability, that are indicators of truth. Accordingly, a feature of belief is an epistemic feature if it is at least some indication that the belief is true.
Many beliefs have lots of positive epistemic features; many beliefs are quite rational, quite justified, very probably true, highly warranted, and so on. However, most people, at least in some moments, do not want to rest content with just being rational because even a rational belief can be false. To wit, one can be very conscious, careful, and logical in forming a belief, and so be rational in holding the belief; but it still might be false. Arguably, one's ultimate ambition for his or her beliefs is knowledge. If one does know something, then not only is one justified, or rational, in a belief, one has the truth. Accordingly, when one is thinking about the epistemic features of one's beliefs, the overarching question is: When does someone have knowledge? When can someone say that he or she has knowledge? Skeptics claim that we cannot have knowledge.
Epistemology includes the study of:
- the epistemic features of belief, such as justification and rationality;
- the origin or sources of such features (and thus the sources of knowledge);
- what knowledge is, i.e., what epistemic features would make a true belief knowledge;
- whether it is possible to have knowledge.
One of the more difficult topics of philosophy is trying to answer, or otherwise deal with, the challenge that one cannot have knowledge. A number of philosophers -- not too many, but some -- have said that we cannot have knowledge. Many philosophers have said that it is very difficult to obtain knowledge, but they usually do not deny that we have it or that we can have it. Not so many philosophers, however, have gone so far as to say that we have no knowledge at all, or (to say something even stronger) that it is impossible to have knowledge.
Foundationalism holds that there are basic beliefs in which you can be certain and that you can be similarly confident in other beliefs derived rigorously from these. The most famous example of this is Descartes' statement cogito ergo sum ("I think therefore I am"), by which he meant that it is impossible to doubt one's own existence. Others have responded that a person's observation of his or her own mental activity is not fundamentally different or more reliable than other observations and does not necessarily imply a thinker. The difficulty of foundationalism is that no set of basic beliefs proposed for it are uncontroversial.
Coherentism holds that you are more justified in beliefs if they form a coherent whole with your other beliefs. A common, cheeky, riposte to this is called the "drunken sailors" argument, which points out that two drunken sailors holding each other up may still not be on solid ground. Stated more formally: a set of beliefs can be internally consistent but still not reflect the actual world.
Recently, Susan Haack has attempted to fuse these two approaches into her doctrine of Foundherentalism, which accrues degrees of relative confidence to beliefs by mediating between the two approaches. She covers this in her book Evidence and Inquiry: Towards Reconstruction in Epistemology.
See also: Self-evidence, theory of justification, the regress argument in epistemology, a priori and a posterior knowledge, knowledge, scepticism, Common sense and the Diallelus, social epistemology, aesthetics, ethics, metaphysics, philosophy, ontology, reason, philosophy of science, science education.