Question

One of the traditional goals of epistemology—the branch of philosophy that concerns theories of knowledge—is to identify beliefs that are certain, beyond any doubt. As you will read in Unit 2, this pursuit is the major preoccupation of the famous philosopher, Descartes, who was not satisfied with Plato’s theory. Plato believed that only human reasoning could lead to genuine knowledge, beliefs that can be held with certitude.   For Plato, of course, these supposedly indubitable beliefs concern the Forms—a metaphysical theory that many subsequent philosophers have rejected.

Accordingly, the question for you is: what, if anything, do you know with absolute certainty? On what basis can you justify this conviction? How might a sceptic challenge your belief?

Answer 1

The term “epistemology” comes from the Greek “episteme,” meaning “knowledge,” and “logos,” meaning, roughly, “study, or science, of.” “Logos” is the root of all terms ending in “-ology” – such as psychology, anthropology – and of “logic,” and has many other related meanings.

The word “knowledge” and its cognates are used in a variety of ways. One common use of the word “know” is as an expression of psychological conviction. For instance, we might hear someone say, “I just knew it wouldn’t rain, but then it did.” While this may be an appropriate usage, philosophers tend to use the word “know” in a factive sense, so that one cannot know something that is not the case. (This point is discussed at greater length in section 2b below.)

Even if we restrict ourselves to factive usages, there are still multiple senses of “knowledge,” and so we need to distinguish between them. One kind of knowledge is procedural knowledge, sometimes called competence or “know-how;” for example, one can know how to ride a bicycle, or one can know how to drive from Washington, D.C. to New York. Another kind of knowledge is acquaintance knowledge or familiarity; for instance, one can know the department chairperson, or one can know Philadelphia.

Epistemologists typically do not focus on procedural or acquaintance knowledge, however, instead preferring to focus on propositional knowledge. A proposition is something which can be expressed by a declarative sentence, and which purports to describe a fact or a state of affairs, such as “Dogs are mammals,” “2+2=7,” “It is wrong to murder innocent people for fun.” (Note that a proposition may be true or false; that is, it need not actually express a fact.) Propositional knowledge, then, can be called knowledge-that; statements of propositional knowledge (or the lack thereof) are properly expressed using “that”-clauses, such as “He knows that Houston is in Texas,” or “She does not know that the square root of 81 is 9.” In what follows, we will be concerned only with propositional knowledge.

Propositional knowledge, obviously, encompasses knowledge about a wide range of matters: scientific knowledge, geographical knowledge, mathematical knowledge, self-knowledge, and knowledge about any field of study whatever. Any truth might, in principle, be knowable, although there might be unknowable truths. One goal of epistemology is to determine the criteria for knowledge so that we can know what can or cannot be known, in other words, the study of epistemology fundamentally includes the study of meta-epistemology (what we can know about knowledge itself).

A distinction closely related to the previous one is that between “occurrent” and “dispositional” knowledge. Occurrent knowledge is knowledge of which one is currently aware. If one is working on a problem and suddenly sees the solution, for example, one can be said to have occurrent knowledge of it, because “seeing” the solution involves being aware of or attending to it. In contrast, dispositional knowledge, as the term suggests, is a disposition, or a propensity, to behave in certain ways in certain conditions. Although Smith may not now be thinking of his home address, he certainly knows it in the sense that, if one were to ask him what it is, he could provide it. Thus, one can have knowledge of things of which one is not aware at a given moment.

René Descartes is a philosopher, mathematician, and scientist that was born in France in 1596. Although he was also a scientist and a mathematician, he's primarily known for his philosophical ponderings. Most notably, Meditations on First Philosophy. In Meditations...', Descartes set about seeking doubt in everything that he knew: His family, friends, the food he ate, and the clothes he wore. Even everything he'd learned in school.

Plato

Plato accepted the Parmenidean constraint that knowledge must be unchanging. One consequence of that view, as Plato pointed out in the Theaetetus, is that sense experience cannot be a source of knowledge, because the objects apprehended through it are subject to change. To the extent that humans have knowledge, they attain it by transcending sense experience in order to discover unchanging objects through the exercise of reason.

Plato, marble portrait bust, from an original of the 4th century BCE; in the Capitoline Museums, Rome.G. Dagli Orti—DeA Picture Library/Learning Pictures

The Platonic theory of knowledge thus contains two parts: first, an investigation into the nature of unchanging objects and, second, a discussion of how those objects can be known through reason. Of the many literary devices Plato used to illustrate his theory, the best known is the allegory of the cave, which appears in Book VII of the Republic. The allegory depicts people living in a cave, which represents the world of sense-experience. In the cave, people see only unreal objects, shadows, or images. Through a painful intellectual process, which involves the rejection and overcoming of the familiar sensible world, they begin an ascent out of the cave into reality. That process is the analogue of the exercise of reason, which allows one to apprehend unchanging objects and thus to acquire knowledge. The upward journey, which few people are able to complete, culminates in the direct vision of the Sun, which represents the source of knowledge.