The Linguistic Turn
The linguistic turn in twentieth-century philosophy refers to the rising influence of logical positivism (especially the work of Rudolf Carnap [1891–1970]), as well as positivism's discontents (Willard Van Orman Quine [1908–2000]), heretics (Ludwig Wittgenstein [1889–1951]), and satellites (Bertrand Russell [1872–1970], Karl Popper [1902–1994]). The movement began in German-speaking countries in the 1930s but rose to predominance in English-language philosophy after World War II. It mingled with an independently evolved linguistic analysis and so-called ordinary-language philosophy, as in the work of George Edward Moore (1873–1958), J. L. Austin (1911–1960), and Gilbert Ryle (1900–1976). For all these thinkers, everything in philosophy is a matter of language. The problem of knowledge is a problem of semantic analysis: how is the word used? What is the language game, the logic of the concept?
In a widely discussed article, "Is Justified True Belief Knowledge?" (1963), Edmund Gettier claimed to prove that knowledge is not conceptually equivalent to justified true belief. Gettier's paper shows the style of the then-new analytic approach, using contrived scenarios as logical counterexamples to the definition of knowledge as justified true belief. The counterexamples usually work by drawing a reasonable inference from a justified though false belief, inferring something true by accident. Suppose I believe that a neighbor, Jones, owns a Ferrari. I have evidence: it is parked by his house, I see him in it, and so on. Because I believe Jones owns a Ferrari, and because Jones is my neighbor, I infer that a neighbor owns a Ferrari. Jones, however, does not own the car, which is owned by my neighbor on the other side, who, unknown to me, works with Jones. Still, it is true that a neighbor owns a Ferrari, and I believe that truth on good evidence. I have a justified true belief, but do I know that a neighbor owns a Ferrari? To most people it seems wrong to say so, especially since the neighbor I am thinking of is not the neighbor who owns the automobile. Apparently, then, knowledge is not justified true belief.
Gettier's argument spurred an academic industry. The problem was to render the justified-true-belief formula invulnerable to Gettier-type cases, or replace this "classical" definition of knowledge with something equally plausible and immune to counterexample. Nothing memorable came of it. And contrary to what is often said, the definition of knowledge as justified true belief is not in any sense "classical." It has never been widely accepted and first entered philosophical discussion (in Plato's Theaetetus) as a refuted theory.
Between Gettier-inspired concerns about the analysis of knowledge and the project of refuting the skeptic, epistemologists fell into two broad camps, depending on whether they considered knowledge to require an element of justification or understanding, or whether, contrary to tradition, true belief might be enough. The idea that knowledge requires only true belief, provided the cause of the belief is appropriate or reliable, is known as externalism. Such theories reject the traditional assumption that knowledge requires the knower to understand the reason why a belief is true. They thereby finesse both the Gettier problem and the problem of skepticism. If knowing does not require understanding, then neither must a person who knows be able to refute the skeptic. And if knowledge does require that the cause of belief be reliable, even if the reasons for trust are unknown to the knower, then Gettier-scenario counterexamples fail due to an unreliable source for the (accidentally) true belief.
The heyday of linguistic philosophy had passed by 1980. The movement had led to little in the theory of knowledge. Pure conceptual or semantic analysis was largely abandoned. Exchanging those discredited methods for the richer data of the sciences, Quine called for a "naturalized epistemology." The idea was to reframe the theory of knowledge in terms of empirical hypotheses about the neurological, cognitive, and evolutionary matrix of human knowledge. Quine's project attracted many followers, and Analytic philosophers formed new and often quite deep alignments with scientific research in these areas.
A second trend in post-linguistic-analysis philosophy is a movement of internal critique, a deconstructive diagnosis of epistemology as a pseudoproblem. Wittgenstein inspired this turning of philosophy upon itself, claiming to find conceptual confusion and intellectual neurosis everywhere. The autocritique of epistemology was led by Richard Rorty's Philosophy and the Mirror of Nature (1979). Rorty finds the very idea of a "theory of knowledge" premised on an untenable concept of mental representation as a kind of "correspondence" or "isomorphism" with things in themselves.
The word cognition relates to the ways in which people (and other species) draw information from the world, combine and interpret it, and make decisions about the information. Identifying this cognitive, information-processing function with knowledge seemed to open the way to a biological, evolutionary theory of knowledge, as by Konrad Lorenz (1903–1989). Later evolutionary accounts usually make two claims. The first is that human knowledge is an evolved adaptation, an outcome of natural selection. The second is that any adaptation of any species is a kind of knowledge, that evolutionary adaptation is the primary way of knowing the world. In these accounts an insect's camouflage coloration is knowledge of its environment; the fleshy water-conserving cactus stem "knows" that water is locally scarce; the shape of the hummingbird beak expresses knowledge of the structure of the flowers it lives on. Human knowledge is a special case of this primary and ubiquitous biological knowledge of adaptation.
By the latter twentieth century feminism had established a presence in the academy, criticizing and developing theories in several areas of philosophical research, including the theory of knowledge. Most feminists have nothing good to say about what has been done in epistemology. Presuming to speak in a universal voice, philosophical theories of knowledge are gendered and do not know it. Feminists challenge epistemology's concept of knowledge (as objective, transcendent, disinterested) and its conception of the knower (as autonomous, self-interested, isolated). They deepen the discontent of the postpositivist philosophy of science and urge points similar to the sociologists of knowledge. Distinctive is the attention to early experience, emotion, racism, class, and, above all, gender as vectors of knowledge repressed from a sexist epistemology.