Who Are Some Key Figures in Epistemology?

It is difficult to imagine a major thinker in Western philosophy who does not have an epistemology—the study of what knowledge is, how we get it, and how much of it we can have. Influential figures in the history of Western philosophy provide very different answers to these questions. Some maintain that knowledge is a rare intellectual achievement, something hard-earned through philosophical reflection. Others maintain that knowledge is nearly as common as belief—something we almost cannot help but have. Still others fall somewhere between these poles. In this article we’ll look at where a few influential philosophers from the history of Western philosophy stand along this range of positions.

Thought by many to be the progenitor of Western philosophy, Plato’s (429?–347 B.C.E.) epistemology is distinguished by his theory of Forms, which he believes are the proper objects of knowledge. Think about the property of being rectangular. It’s shared by houses, boxes and classrooms. Plato’s idea is that this property is a universal that is instantiated in these particulars, and this universal is the Form of ‘rectangularity.’ This Form is the proper object of knowledge, then, because it is an unchanging entity underlying the diversity of particulars in which it is instantiated. 

One key question for Plato is whether and how we acquire knowledge of the Forms. Here he offers his famous theory of recollection, which suggests we enjoyed this knowledge before our embodiment, and our task is to recollect it through philosophical reflection. 

Descartes’ Epistemology Famously Appeals to God

In his Meditations on First Philosophy Descartes applies his ‘method of doubt’ to uncover what, if anything, he really knows. Applied rigorously, this method leaves only the cogito—I think, I am—as the foundation of knowledge for Descartes. To win back knowledge of everything from mathematics to the natural world, Descartes believes he needs a guarantor of the reliability of his intellectual and perceptual faculties. This guarantor is God, whom Descartes argues could not be a deceiver on pain of imperfection, and therefore can be trusted to have created Descartes to be a being whose intellectual faculties are reliable. 

The Scottish philosopher David Hume (1711–1776) is among the most famous of the empiricists in the early modern period of philosophy. Empiricism is the view that the source of our knowledge is experience. (Contrast this with Plato’s and Descartes’ rationalism, which roughly holds the source of our knowledge is reason.) Hume’s empiricism is distinguished by what he calls the copy principle. This is the idea that our ‘simple ideas’ (like, say, our idea of a shade of blue) are copies of impressions upon our senses, such as from seeing the blue sky. Complex ideas, such as that of a blue house, are combinations of simple ideas that are traceable back to impressions. 

One important consequence of Hume’s empiricism is his skepticism. For Hume believes that we are not directly acquainted with external objects, but rather only with sense impressions of them (the same applies to the ‘necessary connections’ that Hume believes constitute causal relations). The consequence is that there is no non-question-begging way to infer the existence of external objects from these sense impressions. Instead, Hume believes, their existence is beyond the grasp of reason and is left to belief as a matter of our animal natures. 

Edmund Gettier Challenges the Traditional View of Knowledge

So far we have looked at major figures in the history of Western philosophy, who are distinguished by having far-reaching, almost systematic philosophies. Let’s conclude by turning to a figure in the twentieth century who, in a short paper, managed to turn over the longstanding view that knowledge is justified true belief. 

This account of knowledge—known as the ‘tripartite account’ because of its three parts—holds that someone has knowledge whenever they have a belief that is true and also justified, which roughly means based on evidence or a reason. Gettier disrupted this classical picture by showing counterexamples in which one satisfies these three conditions but still does not have knowledge because her belief is true only by luck. 

For example, imagine you’re out fishing and take yourself to see a large rock bass a few meters away from the boat. After coming closer and casting your line, however, you realize that what you saw was just a reflection on the water that appeared rock-bass-like. To your astonishment, however, just beside this reflection is an actual rock bass. Gettier’s analysis of this situation says that you believe there is a rock bass, the appearance justifies your belief, and your belief is true, but only by luck. The tripartite account of knowledge, however, says you know there is a rock bass a few meters from the boat. 

The point to take away is that either the justification condition must be strengthened to exclude such cases of epistemic luck, or the tripartite analysis of knowledge is false.