The Grey Man
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Karl Popper and the Friesian Trilemma
Karl Popper, for those of you who are unfamiliar with him, is one of the most prominent philosophers of the 20th century and the most important commentator on the scientific method since Bacon. His chief epistemological work, The Logic of Scientific Discovery, defended a thesis that is now taken for granted by empirical researchers of all kinds: that scientific experiments are conducted with the aim, not of verifying theories, but of falsifying them; and that, therefore, a scientific theory is, perforce, one that makes at least one statement that could hypothetically be proven false by a suitable test.
For example, if all ravens hitherto observed were black and I made the claim that “some ravens are black,” my theory would be unscientific because it doesn’t make any testable predictions, but merely takes stock of what has already been observed. If, on the other hand, I claimed that “all ravens are black,” my theory would be scientific, and not because it can be proven right—indeed, it can’t possibly be proven right because, no matter how many black ravens we find, there remains a possibility that somewhere, somewhen, there is a white raven, or a blue one, or purple, and so on. A scientific theory, then, is one that can be revised on the grounds of falsifying observations.
Observations: if scientific theories are houses built with a view to future renovation, then these are the bedrock upon which the whole edifice of science rests. Just as no house can stand whose foundations are not supported by firm ground, so no scientific theory is justified if it is not based on experience, and this invites a question that Popper’s falsificationist doctrine cannot answer: How can scientific theories be based on experience? Objects of observation are material—ravens, rocks, houses, etc. are all particular pieces of matter individuated by their unique locations, shapes, and sensible qualities—whereas theories are purely formal combinations of symbols, so how can the former be the basis of the latter? How can real things ground ideas?
Popper recalls that the post-Kantian philosopher Jakob Fries asked this question long before he did:
In other words, if our scientific theories are to be established on firm ground, we must find a solution to the Friesian trilemma, which is the choice between:
I say “ostensibly” because Popper has clearly chosen Friesian psychologism, albeit with a difference: whereas Fries taught that scientific theories are grounded in observation qua observation, Popper says that they are grounded in observation qua object of observation. In other words, Fries’s psychologism is introverted and Popper’s is extraverted—Popper is Fries turned inside-out. One says that scientific theories are creations of the mind, the other that they are products of the human brain…
…and both are right. By rejecting Fries’ introspective psychologism and replacing it with his own naturalistic psychologism, Popper has forgotten Kant’s inestimable distinction between the empirical character and the intelligible character of man. More precisely, he has forgotten that the naturalistic, or empirical, description of man does not contradict or compete with his description as he is in himself, but complements it. Like too many philosophers of the post-Enlightenment age, he has forgotten that he has, besides a body, a soul.
Karl Popper, for those of you who are unfamiliar with him, is one of the most prominent philosophers of the 20th century and the most important commentator on the scientific method since Bacon. His chief epistemological work, The Logic of Scientific Discovery, defended a thesis that is now taken for granted by empirical researchers of all kinds: that scientific experiments are conducted with the aim, not of verifying theories, but of falsifying them; and that, therefore, a scientific theory is, perforce, one that makes at least one statement that could hypothetically be proven false by a suitable test.
For example, if all ravens hitherto observed were black and I made the claim that “some ravens are black,” my theory would be unscientific because it doesn’t make any testable predictions, but merely takes stock of what has already been observed. If, on the other hand, I claimed that “all ravens are black,” my theory would be scientific, and not because it can be proven right—indeed, it can’t possibly be proven right because, no matter how many black ravens we find, there remains a possibility that somewhere, somewhen, there is a white raven, or a blue one, or purple, and so on. A scientific theory, then, is one that can be revised on the grounds of falsifying observations.
Observations: if scientific theories are houses built with a view to future renovation, then these are the bedrock upon which the whole edifice of science rests. Just as no house can stand whose foundations are not supported by firm ground, so no scientific theory is justified if it is not based on experience, and this invites a question that Popper’s falsificationist doctrine cannot answer: How can scientific theories be based on experience? Objects of observation are material—ravens, rocks, houses, etc. are all particular pieces of matter individuated by their unique locations, shapes, and sensible qualities—whereas theories are purely formal combinations of symbols, so how can the former be the basis of the latter? How can real things ground ideas?
Popper recalls that the post-Kantian philosopher Jakob Fries asked this question long before he did:
Popper said:The problem of the basis of experience has troubled few thinkers so deeply as Fries. He taught that, if the statements of science are not to be accepted dogmatically, we must be able to justify them. If we demand justification by reasoned argument, in the logical sense, then we are committed to the view that statements can be justified only by statements. The demand that all statements be logically justified (described by Fries as a ‘predilection for proofs’) it is therefore bound to lead to an infinite regress. Now, if we wish to avoid the danger of dogmatism as well as an infinite regress, then it seems as if we could only have recourse to psychologism, i.e., the doctrine that statements can be justified not only by statements but also by perceptual experience. Faced with this trilemma—dogmatism vs. infinite regress vs. psychologism—Fries, and with him almost all epistemologists who wished to account for our empirical knowledge, opted for psychologism. In sense-experience, he taught, we have ‘immediate knowledge’: by this immediate knowledge, we may justify our ‘mediate knowledge’—knowledge expressed in the symbolism of some language. And this mediate knowledge includes, of course, the statements of science.
In other words, if our scientific theories are to be established on firm ground, we must find a solution to the Friesian trilemma, which is the choice between:
- the uncritical acceptance of certain statements as if they were mathematical axioms;
- the doomed attempt to justify our statements by other statements ad infinitum; or
- the uncritical acceptance of certain statements because “I’m pretty sure they’re true.”
Popper said:The basic statements at which we stop, which we decide to accept as satisfactory, and as sufficiently tested, have admitted the character of dogmas, but only in so far as we may desist from justifying them by further arguments (or by further tests). But this kind of dogmatism is innocuous since, should the need arise, these statements can easily be tested further. I admit that this too makes the chain of deduction in principle infinite. But this kind of ‘infinite regress’ is also innocuous since in our theory there is no question of trying to prove any statements by means of it. And finally, as to psychologism: I admit, again, that the decision to accept a basic statement, and to be satisfied with it, is causally connected with our experiences—especially with out perceptual experiences. But we do not attempt to justify basic statements by these experiences. Experiences can motivate a decision, and hence an acceptance or a rejection of a statement, but a basic statement cannot be justified by them—no more than by thumping the table.
I say “ostensibly” because Popper has clearly chosen Friesian psychologism, albeit with a difference: whereas Fries taught that scientific theories are grounded in observation qua observation, Popper says that they are grounded in observation qua object of observation. In other words, Fries’s psychologism is introverted and Popper’s is extraverted—Popper is Fries turned inside-out. One says that scientific theories are creations of the mind, the other that they are products of the human brain…
…and both are right. By rejecting Fries’ introspective psychologism and replacing it with his own naturalistic psychologism, Popper has forgotten Kant’s inestimable distinction between the empirical character and the intelligible character of man. More precisely, he has forgotten that the naturalistic, or empirical, description of man does not contradict or compete with his description as he is in himself, but complements it. Like too many philosophers of the post-Enlightenment age, he has forgotten that he has, besides a body, a soul.