II. Popper's Conception of Knowledge
According to the Encyclopedia of Philosophy (Vol. IV, p. 345), the most widely accepted definition of knowledge is "justified true belief". On Popper's view none of these terms describe important characteristics of knowledge.
First of all, propositions need not be believed by anyone. Suppose the writer of an encyclopedia dies and no one ever reads her article; nevertheless, the information therein remains knowledge although no one actively believes it. Or, to cite one of Popper's examples, consider a table of logarithms generated by a computer program. It may turn out that certain items of the table are never read by any human. Yet they are part of mathematical knowledge.
So for Popper the genus of knowledge is, objective propositional content, not the subjective attitude towards propositions. Knowledge may be encoded in human brains, but it may also be inscribed in books, photographs, cave paintings, or books, software. Whether any one actively believes the proposition is irrelevant to its status as knowledge. (As my old chemistry teacher used to tell us, "If you want to be a good chemist, don't make a handbook out of your head!")
Knowledge items for Popper need not be believed, but mustn't they at least be worthy of rational belief? Shouldn't they be true and justifiable? Here again Popper departs from the traditional conception.
Knowledge claims need not be true, Popper argues and he cites two sorts of examples. First of all, many of the most important propositions in science are literally false - e.g., all of the laws of classical physics and chemistry. Matter is not conserved, planets do not travel in perfect elipses, atoms are not indivisible, and not all molecules of water are alike. Neither are the claims of the theories which replaced classical science, such as Relativity Theory and Quantum Mechanics, without flaw. If we were to follow the traditional epistemological delimitation of knowledge to true propositions, it might well turn out that there is no scientific knowledge. (Cf. Cartwright, How the Laws of Physics Lie)
Popper goes on to argue that many of the most basic bits of common-sense knowledge are also false. The sun does not rise every twenty-four hours, at least not in the Land of the Midnight Sun and bread can be poisonous, if it is made from ergotic wheat.
But if we admit the existence of false knowledge claims shouldn't we at least require that in order to count as knowledge in a particular historical context a statement must have been well-confirmed by the evidence available at that time? Shouldn't we insist that one should be justified in believing knowledge propositions, even if later evidence may cause us to reverse our appraisal of their truth value?
Some of the details of Popper's criticisms of various justificationist epistemologies will emerge below. Suffice it to say here that with respect to the logical positivists Popper argues that there is no infallible empirical base - the most trivial sounding observation report, such as "Here is a glass of water", contains so many untested implications, such as, "If you were to drop it, the water would spill while the glass would break" or "If you were to cool it, the water would turn into ice," that it is impossible to verify them all. Furthermore, even if we were to take some set of observation reports as indubitable evidence, Popper follows Hume in arguing that they can never provide the kind of logical justificatory support assumed by inductivist philosophers.
But if we give up these traditional epistemological requirements, how are we to distinguish those propositions which are part of knowledge from random sentences generated by the apocryphal monkey at the typewriter, or, more realistically, from the outputs of programs such as Rachter? Is Stove (Popper and After) right in claiming that Popper has so changed the meaning of knowledge by completely denying its sense of cognitive success and achievement that it is misleading for him to continue to use it? What, according to Popper, are the delimiters of knowledge?
I know of no place where Popper gives a short, italicized definition of knowledge but we can construct one from his writings.
First of all if we are prepared to identify knowledge with our best science, he does give an explicit minimal characterization of a scientific claim - it is one which can be subjected to empirical test - and our best scientific claims are falsifiable propositions which are not false as far as we know but which have successfully passed severe empirical testing. Such a tri-partite definition would replace the old justified-true-belief account by replacing each of its components.
However, Popper often uses knowledge in a looser sense when he speaks of 'background knowledge' and its role in setting problems or appraising the severity of a test. These propositions are assumed to be unproblematic in a particular problem-situation (C. & R, p. 238) but there is no suggestion that they each have been carefully tested. In fact to demand systematic testing would lead to another falsificationist regress almost as vicious as the inductivist one. Neither must critical scrutiny be limited to empirical testing. Unlike the positivists, Popper would never consider excluding mathematics or philosophy from knowledge.
The proper conclusion to draw, I think, is that Popper does not try to delimit knowledge propositions because on his account it makes no sense to do so. No propositions receive permanent gold stars on Popper's account. All claims are conjectural although some have been more carefully scrutinized than others. In some contexts a proposition will be temporarily accepted; in others it may be challenged. What we can do at any point is to open the case on any claim and review its test record, its logical compatibility with other statements, its explanatory power, what problems it helps solve, what problems it generates, etc. But it would be fruitless to demand that we always start by reviewing the credentials of every proposition in sight.
In the essays collected together in Objective Knowledge, Popper stresses the similarities between the growth of knowledge in the scientific community, animal learning, and the evolution of biological species! There is a sense in which three of these processes involve problem-solving, trial solutions, and error elimination. (Popper makes some lovely provocative remarks in which he compares Einstein and an amoeba and includes a bird's nest in his World-3, where objective knowledge resides!) Of course, there are other places where Popper stresses the unique features of science (more of this later) but by separating knowledge from human consciousness it is very easy for Popper to posit that knowledge is encoded in genotypes and guppies as well as in geniuses!
Let us now look in s little more detail at the parallels Popper draws between biological evolution, animal learning, and scientific inquiry, three processes which instantiate his general schema:
P -> TS -> EE -> P '
P stands for problem, which is to be understood in an objective sense and does not imply that the entity which "has" the problem is conscious of it. In the biological domain, species face problems connected with survival and reproductive success, such as the problems of escaping predators, raising young, finding food, mates, etc.
TS stands for tentative solution, such as the information encoded within a new genotype within the species' pool. EE, or error elimination occurs if the phenotype bearing the new genotype dies without reproducing (or reproduces at a lower rate than its con-specifies).
The outcome of reiterations of the TS and EE steps is a species better adapted to its environment, but new problems (P ') will typically lead to a repetition of the whole selection process.
When the schema is applied to animal learning it looks fairly similar to Skinnerian operant conditioning. [See Skinner's "Selection by Consequences"] In response to the "problem" posed by hunger pangs, or whatever, the animal engages in exploratory behavior (thus proposing a tentative "solution"). Unsuccessful solutions lead to no food, or even pain, and are extinguished. When a new behavior is successful, however, it becomes part of the individual animal's patterned response to that type of problem-situation. New problems then lead to more learning.
The application of the schema to scientific inquiry is quite straight-forward. Scientists propose falsifiable conjectures in response to problems arising within their knowledge situation, which are then subjected to empirical test. False hypotheses are thereby eliminated and the scientist is then free to confront new cognitive problems.
FIGURE 3
These three instantiations of the schema are summarized in Figure 3. Let us now comment on some of the important dissimilarities
between scientific inquiry and these other selection processes. The crucial difference, as Popper notes, is that in science "our mistaken theories die in our stead". If a species fails to solve a survival problem, it goes extinct. If a rat fails to find a path through a maze, it goes hungry. In both cases, the consequences of error (or success for that matter) have a direct physical effect on organisms. The scientist, on the other hand, may experience elation or disappointment as a result of empirical testing but these psychological reactions are not simply coupled within the selection process. For example, I may derive satisfaction from designing a clever test which refutes a hypothesis even when the hypothesis was of my own creation. And to the extent to which science is a "friendly hostile" competition between ideas (to use Popper's phrasing), there could even be a division of labor between creation and criticism such that every prediction failure is a personal triumph!
Because the success or failure of a scientific hypothesis can be decoupled from pleasure and pain, the scientist is free both to propose bold conjectural solutions and to test them severely. And the fact that us scientists we are free to choose problems - they are not forced on us by the environment - also allows us to operate less cautiously. Although the evaluation of scientific theories depends crucially on feedback from the environment, human scientists experience relatively little feedback from prediction successes or failures. Contrast the situation of the technologist, e.g., a potter who is trying to solve the problem of how to prevent pots from exploding in the kiln. Here the problem is set by practical considerations. Tentative solutions should be economically viable and may be of such limited scope as to apply only to the local clay and kilns. And it would be absurd to push any solution which appears to work to extremes. Prediction failures cost time and money and so the potter will theorize conservatively. Thus, although the potter, unlike the animal, can articulate the hypotheses under test and use information in books to criticize them, the potter's situation is more like the animal's than the scientist's because she or he is directly rewarded or punished according to the success of the tentative solution.
The scientist's relative freedom from personal repercussions sounds wonderful and liberating, but it can also pose the following problem. Note that on the biological or animal level it is not possible for the organism to "ignore" refutations because it is causally connected to the environment. A dogmatic potter may engage in a process of psychological denial of the pot shards from exploding pots but will soon go out of business. But an individual scientist may evade the elimination of erroneous theories by using ad hoc modifications or conventionalist strategems with impunity. To do so is like cheating as Solitaire - it may not be as much fun, but nothing keeps you from doing it - except one's internalized standards of fair play.
An interesting question, then, is how scientific institutions and traditions can best reward (or punish!) scientists' activities as they engage in scientific inquiry. (For example, how do we discourage people from publishing non-reproducible experimental results while encouraging them to produce interesting detailed conjectures which may well be falsified?)