I’ve generally found Paul Feyerabend’s position on science to be a bit too extreme. Here is one provocative statement in the analytical index of Against Method:
Thus science is much closer to myth than a scientific philosophy is prepared to admit. It is one of the any forms of thought that have been developed by man, and not necessarily the best. It is conspicuous, noisy, and impudent, but it is inherently superior only for those who have already decided in favour of a certain ideology, or who have accepted it without having ever examined its advantages and its limits. And as the accepting and rejecting of ideologies should be left to the individual it follows that the separation of state and church must be supplemented by the separation of state and science, that most recent, most aggressive, and most dogmatic religious institution. Such a separation may be our only chance to achieve a humanity we are capable of, but have never fully realised.
This isn’t a baseless misreading of Feyerabend. In fact, it isn’t a bad paraphrase of Against Method. But it isn’t the whole story either. And at bottom, I don’t think it is accurate to say that Feyerabend rejects the idea of scientific rationality. Rather, he rejects one common interpretation of that notion: the view that scientific rationality can be reduced to a set of universal canons of investigation and justification, and that there is a neutral and universal set of standards of inference that decisively guide choice of scientific theories and hypotheses. So I think it is better to understand Feyerabend as presenting an argument against a certain view in the philosophy of science rather than against science itself.
First, Feyerabend is a philosopher and historian of science who himself demonstrates a great deal of respect for empirical and historical detail. The facts matter to Feyerabend, in his interpretation of the history of science. He establishes his negative case with painstaking attention to the details of the history of science — Newton, optics, quantum mechanics. This is itself a kind of empirical reasoning about the actual intellectual practices of working scientists. But if Feyerabend were genuinely skeptical of the enterprise of offering evidence in favor of claims, this work would be pointless.
Second, his own exposition of several scientific debates demonstrates a realist’s commitment to the issues at stake. Take his discussion of the micro-mechanisms of reflection and light “rays”. If there were in principle no way of evaluating alternative theories of these mechanisms, it would be pointless to consider the question. But actually, Feyerabend seems to reason on the assumption that one theory is better than another, given the preponderance of reasons provided by macro-observations and mathematical-physical specification of the hypotheses.
The final reply to the question put in the title is therefore as follows. A good empiricist will not rest content with the theory that is in the centre of attention and with those tests of the theory which can be carried out in a direct manner. Knowing that the most fundamental and the most general criticism is the criticism produced with the help of alternatives, he will try to invent such alternatives. (102)
So as a historian of science, Feyerabend seems to have no hesitation himself to engage in empirical reasoning and persuading, and he seems to grant a degree of locally compelling reasoning in the context of specific physical disputes. And he appears to presuppose a degree of epistemic importance — always contestable — for a body of scientific observation and discovery.
It is indubitable that the application of clear, well-defined, and above all ‘rational’ rules occasionally leads to results. A vast number of discoveries owe their existence to the systematic procedures of their discoverers. But from that, it does not follow that there are rules which must be obeyed for every cognitive act and every scientific investigation. On the contrary, it is totally improbable that there is such a system of rules, such a logic of scientific discovery, which permeates all reasoning without obstructing it in any way. The world in which we live is very complex. Its laws do not lay open to us, rather they present themselves in diverse disguises (astronomy, atomic physics, theology, psychology, physiology, and the like). Countless prejudices find their way into every scientific action, making them possible in the first place. It is thus to be expected that every rule, even the most ‘fundamental’, will only be successful in a limited domain, and that the forced application of the rule outside of its domain must obstruct research and perhaps even bring it to stagnation. This will be illustrated by the following examples. (138)
The idea that science can, and should, be run according to fixed and universal rules, is both unrealistic and pernicious. It is unrealistic, for it takes too simple a view of the talents of man and of the circumstances which encourage, or cause, their development. And it is pernicious, for the attempt to enforce the rules is bound to increase our professional qualifications at the expense of our humanity. In addition, the idea is detrimental to science, for it neglects the complex physical and historical conditions which influence scientific change. It makes our science less adaptable and more dogmatic: every methodological rule is associated with cosmological assumptions, so that using the rule we take it for granted that the assumptions are correct. Naive falsificationism takes it for granted that the laws of nature are manifest and not hidden beneath disturbances of considerable magnitude. Empiricism takes it for granted that sense experience is a better mirror of the world than pure thought. Praise of argument takes it for granted that the artifices of Reason give better results than the unchecked play of our emotions. Such assumptions may be perfectly plausible and even true. Still, one should occasionally put them to a test. Putting them to a test means that we stop using the methodology associated with them, start doing science in a different way and see what happens. Case studies such as those reported in the preceding chapters show that such tests occur all the time, and that they speak against the universal validity of any rule. All methodologies have their limitations and the only ‘rule’ that survives is ‘anything goes’.
(Here is an online version of the analytical contents and concluding chapter of Against Method. And here is a link to an article by John Preston on Feyerabend in the Stanford Encyclopedia of Philosophy.)