Reviewing some Popper writing re justificationism and rejecting positive arguments. My basic goal is to check that he was fully opposed to positive arguments. I think that’s his position but haven’t reread him much for years.
Bolds are added by me.
The way in which knowledge progresses, and especially our scientific knowledge, is by unjustified (and unjustifiable) anticipations, by guesses, by tentative solutions to our problems, by conjectures . These conjectures are controlled by criticism; that is, by attempted refutations , which include severely critical tests. They may survive these tests; but they can never be positively justified: they can be established neither as certainly true nor even as ‘probable’ (in the sense of the probability calculus). Criticism of our conjectures is of decisive importance: by bringing out our mistakes it makes us understand the difficulties of the problem which we are trying to solve. This is how we become better acquainted with our problem, and able to propose more mature solutions: the very refutation of a theory—that is, of any serious tentative solution to our problem—is always a step forward that takes us nearer to the truth. And this is how we can learn from our mistakes.
[skipping one paragraph]
Those among our theories which turn out to be highly resistant to criticism, and which appear to us at a certain moment of time to be better approximations to truth than other known theories, may be described, together with the reports of their tests, as ‘the science’ of that time. Since none of them can be positively justified, it is essentially their critical and progressive character—the fact that we can argue about their claim to solve our problems better than their competitors— which constitutes the rationality of science.
This, in a nutshell, is the fundamental thesis developed in this book
The first, the false idea, is that we must justify our knowledge, or our theories, by positive reasons, that is, by reasons capable of establishing them, or at least of making them highly probable; at any rate, by better reasons than that they have so far withstood criticism. This idea implies, I suggest, that we must appeal to some ultimate or authoritative source of true knowledge
For this next quote, I omitted two sources:
Aristotle meant by ‘induction’ ( epagōgē ) at least two different things which he sometimes links together. One is a method by which we are ‘led to intuit the general principle’. The other is a method of adducing (particular) evidence—positive evidence rather than critical evidence or counter-examples.
The members of the first group—the verificationists or justificationists—hold, roughly speaking, that whatever cannot be supported by positive reasons is unworthy of being believed, or even of being taken into serious consideration.
they [verificationists or justificationists] demand that we should accept a belief only if it can be justified by positive evidence ; that is to say, shown to be true, or, at least, to be highly probable.
the rationality of science lies not in its habit of appealing to empirical evidence in support of its dogmas— astrologers do so too—but solely in the critical approach : in an attitude which, of course, involves the critical use, among other arguments, of empirical evidence (especially in refutations). For us, therefore, science has nothing to do with the quest for certainty or probability or reliability. We are not interested in establishing scientific theories as secure, or certain, or probable. Conscious of our fallibility we are only interested in criticizing them and testing them, hoping to find out where we are mistaken; of learning from our mistakes; and, if we are lucky, of proceeding to better theories.
Considering their views about the positive or negative function of argument in science, the first group—the justificationists—may be also nicknamed the ‘positivists’ and the second—the group to which I belong—the critics or the ‘negativists’.
the verificationists laboured in vain to discover valid positive arguments in support of their beliefs, we for our part are satisfied that the rationality of a theory lies in the fact that we choose it because it is better than its predecessors; because it can be put to more severe tests; because it may even have passed them, if we are fortunate; and because it may, therefore, approach nearer to the truth.
The central problem of the philosophy of knowledge, at least since the Reformation, has been this. How can we adjudicate or evaluate the far-reaching claims of competing theories and beliefs? I shall call this our first problem. This problem has led, historically, to a second problem: How can we justify our theories or beliefs? And this second problem is, in turn, bound up with a number of other questions: What does a justification consist of? and, more especially: Is it possible to justify our theories or beliefs rationally : that is to say, by giving reasons—‘positive reasons’ (as I shall call them), such as an appeal to observation; reasons, that is, for holding them to be true, or to be at least ‘probable’ (in the sense of the probability calculus)? Clearly there is an unstated, and apparently innocuous, assumption which sponsors the transition from the first to the second question: namely, that one adjudicates among competing claims by determining which of them can be justified by positive reasons, and which cannot.
I assert (differing, Bartley contends, from all previous rationalists except perhaps those who were driven into scepticism) that we cannot give any positive justification or any positive reason for our theories and our beliefs.
We can often give reasons for regarding one theory as preferable to another. They consist in pointing out that, and how, one theory has hitherto withstood criticism better than another. I will call such reasons critical reasons , in order to distinguish them from those positive reasons which are offered with the intention of justifying a theory, or, in other words, of justifying the belief in its truth.
Critical reasons do not justify a theory, for the fact that one theory has so far withstood criticism better than another is no reason whatever for supposing that it is actually true. But although critical reasons can never justify a theory, they can be used to defend (but not to justify ) our preference for it: that is, our deciding to use it, rather than some, or all, of the other theories so far proposed.
the question of justification, or of the existence of positive reasons
In this way we come to realize that Hume’s epistemological problem—the problem of giving positive justifying reasons, or the problem of justification—might be replaced by the totally different problem of explaining, giving critical reasons, why we prefer one theory to another (or to all others known to us), and ultimately by the problem of critically discussing hypotheses in order to find out which of them is—comparatively—the one to be preferred.
Thus one of the two meta-theories may do no more than sum up the present state of our critical discussion fairly
Popper is trying to explain that saying “I like theory X more than Y because it did better in the critical debate” counts as using negative/critical reasoning. It’s different than “I like theory X more than Y because I have positive reason Z”. He’s saying there’s a difference between objective-level positive claims and comparative meta-level claims about why one theory is better as a result of negative criticism.
there is, again, no attempt on my part to justify positively, or establish, in the traditional sense, that a preference for one theory rather than another is the correct one.
Popper’s saying we don’t establish we’re right, or probably right, or fallibly right, or anything like that. The theories we tentatively accept are fully unjustified. We just found (more quantity and severity of) errors in alternatives. (This is differs from my approach of using decisive arguments while rejecting degree arguments.)
Rather, I replace the question whether we can produce valid reasons (positive reasons) in favour of the truth of a theory by the question whether we can produce valid reasons (critical reasons) against its being true, or against the truth of its competitors.
This is great. Easy to find. Very clear on what I wanted. No positive arguments. Negative arguments only. That’s what Popper says.
David Deutsch (DD) differs. In The Fabric of Reality:
Most contemporary philosophers are crypto-inductivists. What makes matters worse is that (like many scientists) they grossly underrate the role of explanation in the scientific process. So do most Popperian anti-inductivists, who are thereby led to deny that there is any such thing as justification (even tentative justification). This opens up a new explanatory gap in their scheme of things.
DD is correct that Popperians deny all justification. They say all correct arguments are negative, not positive. DD apparently disagreed, disliked that, and tried to diagnose the cause of the error (grossly underrating explanation).
Did Popper grossly underrate explanation? No. DD is smearing him. E.g. RASc:
That my theory, to the extent to which it is accurate, should be of interest to scientists and historians is hardly surprising; for many of them—I believe most of them—share my realist view of the world and also understand the aims of science as I do: to achieve better and better explanations.
as scientists we do not seek highly probable theories but explanations
we do not aim simply at correlations, but at explanations.
The analysis of degrees of explanatory power, and of the relationship between genuine and sham explanation and between explanation and prediction, are examples of problems which are of great interest in this context.
For a scientific theory—an explanatory theory—is, if anything, an attempt to solve a scientific problem, that is to say, a problem concerned or connected with the discovery of an explanation.
Pretending to have discovered that explanations matter is DD’s biggest claim to fame in philosophy. It’s how he most often claims to have improved on Popper. He also tried to campaign on “hard to vary” as if it were a major new insight, not a pretty trivial rewording/implication of “adapted” (which is how knowledge creation works in an evolutionary epistemology like Popper’s – an epistemology that says progress comes from evolving ideas. And what does evolving an idea do? It makes it more adapted. Which means that most random variations make it worse not better. So it’s “hard to vary”.).
So DD claimed to disagree with Popper on something that they agreed on (explanations are really important). But he didn’t like a real disagreement being pointed out (about positive arguments and justification), even though he called Popperians out by name and attacked them in his book.