Epistemology is a branch of philosophy concerned with the possibility and extent of human knowledge. From the Greek episteme, meaning 'knowledge', epistemology concerns every scientific discipline that contributes to the collective efforts of human beings. Epistemological theories seek to discover the nature, origins and limits of human knowledge.
It is safe to say that every philosopher since the beginning of civilization has been concerned to some degree with epistemology. Philosophy is by definition the love of wisdom or the search for true knowledge. With careful scrutiny, philosophers attempt to differentiate truth from belief and appearances. Epistemology aims to provide a foundation for what we consider to be true knowledge.
Many of the most important philosophers, such as Plato and Aristotle, maintained that knowledge is possible. Their epistemology rested on the ability to clearly differentiate between appearance and reality. For Plato, this epistemology was famously illustrated through his theory of forms. Aristotle’s epistemology asserted that true knowledge could be attained through the examination of cause and effect, combined with the application of reason and logic.
Other ancient philosophical schools, notably the skeptics, declared that any and all knowledge is impossible. For them, what we call knowledge is only considered belief at best. In other words, we can never be certain that anything is as it appears. The epistemology of the skeptics elicited a major response from other schools of philosophy, such as the stoics, that were devoted to the idea that knowledge is in fact possible.
Although skepticism was a product of ancient Greece, it experienced a revival in 16th century Europe at the beginning of the Enlightenment. The famous philosopher Renee Descartes, frustrated with the general ignorance of the Middle Ages, worked to form an epistemology that provide proof of the possibility of true knowledge. Descartes began by adopting the skeptic’s stance that we know nothing. By considering all of his previous knowledge to be only belief, his mind was then free to discover the most simple, basic or necessary truth that could not be logically refuted. He called this the “method of doubt.”
Descartes became disheartened after finding that he could doubt just about everything owing to the possibility that all of his experience could be skewed by his perceptions. Every sensation derived from his physical senses could very well be deceiving him. Ultimately, he discovered that in order to be deceived, he must have a mind and be a thinking being, or as he famously stated: Cogito Ergo Sum, or I think, therefore I am. He inferred that, because he could think, he could know for certain that he existed. For Descartes, this truth was the beginning of an epistemology that established the possibility of knowledge.