This is a follow up to Rafe’s post The Stanford Encyclopedia of Philosophy vs Karl Popper in which I reply to the Encyclopedia’s criticism of Popper’s position. The major defect of these criticisms is that they don’t seem to take account of the fact that Popper thought all knowledge was conjectural, and that this was his position since he first wrote Logic of Scientific Discovery.
I will take criticisms 1 and 3 first because they are similar in character. First, criticism 1:
[Popper] asserts that basic statements themselves are open-ended hypotheses: they have a certain causal relationship with experience, but they are not determined by experience, and they cannot be verified or confirmed by experience. However, this poses a difficulty regarding the consistency of Popper’s theory: if a theory X is to be genuinely testable (and so scientific) it must be possible to determine whether or not the basic propositions which would, if true, falsify it, are actually true or false (i.e., whether its potential falsifiers are actual falsifiers). But how can this be known, if such basic statements cannot be verified by experience? Popper’s answer is that ‘basic statements are not justifiable by our immediate experiences, but are … accepted by an act, a free decision’. (Logic of Scientific Discovery, 109). However, and notwithstanding Popper’s claims to the contrary, this itself seems to be a refined form of conventionalism—it implies that it is almost entirely an arbitrary matter whether it is accepted that a potential falsifier is an actual one, and consequently that the falsification of a theory is itself the function of a ‘free’ and arbitrary act.
I think we have to be a bit suspicious here when the author of this article states that Popper’s position is a ‘refined’ form of conventionalism: what refinement is he talking about and does it make a difference? In fact, the refinement makes a very large difference.
Before I answer criticism 1 I will quote criticism 3 because the answers to these two criticisms are related. Criticism 3:
Popper’s final position is that he acknowledges that it is impossible to discriminate science from non-science on the basis of the falsifiability of the scientific statements alone; he recognizes that scientific theories are predictive, and consequently prohibitive, only when taken in conjunction with auxiliary hypotheses, and he also recognizes that readjustment or modification of the latter is an integral part of scientific practice. Hence his final concern is to outline conditions which indicate when such modification is genuinely scientific, and when it is merely ad hoc. This is itself clearly a major alteration in his position, and arguably represents a substantial retraction on his part…
Now, three quotes from Logic of Scientific Discovery. First, his prohibition against ad hoc auxiliary hypotheses from pp. 82-83 (Section 20):
As regards auxiliary hypotheses we propose to lay down the rule that only those are acceptable whose introduction does not diminish the degree of falsifiability or testability of the system in question, but on the contrary increases it. … The introduction of an auxiliary hypothesis should always be regarded as an attempt to construct a new system; and this new system should always be judged according to whether or not it would constitute a real advance in our knowledge of the world.
Popper gives Pauli’s Exclusion Principle (no two electrons can occupy the same quantum state) as an example of a good auxiliary hypothesis.
On page 95, Section 26, Popper argues that statements of singular facts are hypotheses because stating them requires universals:
The statement ‘here is a glass of water’ cannot be verified by any observational experience. the reason is that the universals which appear in it cannot be correlated with any specific sense experience. … By the word ‘glass’, for example, we denote physical bodies that obey a certain law-like behaviour, and the same holds for the word ‘water’.
Finally, on p. 109, Section 29, Popper states that basic statements are left open for criticism and that they are not used to prove anything:
The basic statements at which we stop, which we decide to accept as satisfactory, and as sufficiently tested, have admittedly the character of dogmas, but only insofar 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 statement by means of it. [I have added the italics in the last part of the last sentence for emphasis.]
The answer to these criticisms is that Popper is proposing a theory of conjectural knowledge, and the idea that he is altering his position has no textual basis. So scientific theories are conjectures, experimental results are conjectures, and refutations of our scientific theories are conjectures too. The way we keep science making progress is that scientists try to solve problems by proposing non-ad-hoc solutions to problems, including problems that arise as a result of doingexperiments. A non-ad-hoc theory is testable and it provides an improved understanding of the world if it is true. Scientific theories are controlled by criticism, not by proof and so the fact that we don’t prove anything is flatly irrelevant. No explanation is given in the article for why this position is unsatisfactory. And all of this is explained more clearly in some of Popper’s later work, including his book “Realism and the Aim of Science”.
Now criticism 2:
Popper’s distinction between the logic of falsifiability and its applied methodology does not in the end do full justice to the fact that all high-level theories grow and live despite the existence of anomalies (i.e., events/phenomena which are incompatible with the theories). The existence of such anomalies is not usually taken by the working scientist as an indication that the theory in question is false; on the contrary, he will usually, and necessarily, assume that the auxiliary hypotheses which are associated with the theory can be modified to incorporate, and explain, existing anomalies.
Any scientist worth his salt will try to solve the problem posed by an apparent disagreement between theory and experiment. He may do this by replacing the current theory or by proposing a specific non-ad-hoc auxiliary hypothesis, not just by saying ‘oh well, some auxiliary hypothesis will save my theory’s bacon’. Any scientist who doesn’t want to do this isn’t worth his salt.
On a related note, the author of the article claims that many Marxists wouldn’t be worried by the assertion that Marxism is unscientific because Marxists made ad hoc modifications. If the author of the article is correct in that accusation, then Marxists are a bunch of pseudoscientists.
The poor quality of the criticism section of this article is slightly surprising in the light of the fact that the author manages correctly to state Popper’s position earlier in the same article. Some criticisms earlier in the article, such as criticisms of verismilitude are more accurate, but they also fail to make contact with the most important part of Popper’s position – namely the idea that all knowledge is conjectural and is controlled by criticism. If this is the worst criticism philosophers have to offer, then Popperians don’t have much to worry about.
