In Hans-Hermann Hoppe’s classic article In Defense of Extreme Rationalism: Thoughts on Donald McCloskey’s The Rhetoric of Economics, he has some very interesting observations about falsificationism and empiricism:
Popper would have us throw out any theory that is contradicted by any fact, which, if at all possible, would leave us virtually empty-handed, going nowhere. In recognizing the insoluble connection between theoretical knowledge (language) and actions, rationalism would instead deem such falsificationism, even if possible, as completely irrational. There is no situation conceivable in which it would be reasonable to throw away any theory—conceived of as a cognitive instrument of action—that had been successfully applied in a past situation but proves unsuccessful in a new application—unless one already had a more successful theory at hand. And to thus immunize a theory from experience is perfectly rational from the point of view of an actor. And it is just as rational for an actor to regard any two rivals, in their range of application overlapping theories t1 and t2 as incommensurable as long as there exists a single application in which t1 is more successful than t2 or vice versa. Only if t1 can be as successfully applied as t2 to every single instance to which t2 is applicable but still has more and different applications than t2 can it ever be rational to discard t2. To discard it any earlier, because of unsuccessful applications or because t1 could in some or even in most situations have been applied more successfully, would from the point of view of a knowing actor not be progress but retrogression. And even if t2 is rationally discarded, progress is not achieved by falsifying it, as t2 would actually have had some successful applications that could never possibly be nullified by anything (in the future). Instead, t1 would outcompete t2 in such a way that any further clinging to t2, though of course possible, would be possible only at the price of not being able to successfully do everything that an adherent of t1 could do who could successfully do as much and more than any proponent of t2.
On a related note, he also has some interesting comments about apriorism in the physical sciences: in his “On Praxeology and the Praxeological Foundation of Epistemology” (text at notes 60-62, and note 62; from Economic Science and the Austrian Method), which references Lorenzen, Dingler, Karnbartel, et al., regarding an entire body of “protophysics” –
Further, the old rationalist claims that geometry, that is, Euclidean geometry is a priori and yet incorporates empirical knowledge about space becomes supported, too, in view of our insight into the praxeological constraints on knowledge. Since the discovery of non-Euclidean geometries and in particular since Einstein’s relativistic theory of gravitation, the prevailing position regarding geometry is once again empiricist and formalist. It conceives of geometry as either being part of empirical, aposteriori physics, or as being empirically meaningless formalisms. Yet that geometry is either mere play, or forever subject to empirical testing seems to be irreconcilable with the fact that Euclidean geometry is the foundation of engineering and construction, and that nobody there ever thinks of such propositions as only hypothetically true. 
Recognizing knowledge as praxeologically constrained explains why the empiricist-formalist view is incorrect and why the empirical success of Euclidean geometry is no mere accident. Spatial knowledge is also included in the meaning of action. Action is the employment of a physical body in space. Without acting there could be no knowledge of spatial relations, and no measurement. Measuring is relating something to a standard. Without standards, there is no measurement; and there is no measurement, then, which could ever falsify the standard. Evidently, the ultimate standard must be provided by the norms underlying the construction of bodily movements in space and the construction of measurement instruments by means of one’s body and in accordance with the principles of spatial constructions embodied in it. Euclidean geometry, as again Paul Lorenzen in particular has explained, is no more and no less than the reconstruction of the ideal norms underlying our construction of such homogeneous basic forms as points, lines, planes and distances, which are in a more or less perfect but always perfectible way incorporated or realized in even our most primitive instruments of spatial measurements such as a measuring rod. Naturally, these norms and normative implications cannot be falsified by the result of any empirical measurement. On the contrary, their cognitive validity is substantiated by the fact that it is they which make physical measurements in space possible. Any actual measurement must already presuppose the validity of the norms leading to the construction of one’s measurement standards. It is in this sense that geometry is an a priori science; and that it must simultaneously be regarded as an empirically meaningful discipline, because it is not only the very precondition for any empirical spatial description, it is also the precondition for any active orientation in space. 
62. On the aprioristic character of Euclidean geometry see Lorenzen, Methodisches Denhen, chapters 8 and 9; idem, Normative Logic and Ethics, chapter 5; H. Dingler, Die Grundlagen der Geometrie (Stuttgart: Enke, 1933); on Euclidean geometry as a necessary presupposition of objective, i.e., intersubjectively communicable, measurements and in particular of any empirical verification of non-Euclidean geometries (after all, the lenses of the telescopes which one uses to confirm Einstein’s theory regarding the non-Euclidean structure of physical space must themselves be constructed according to Euclidean principles) see Karnbartel, Erfahrung und Struktur, pp. 132-33; P. Janich, Die Protophysik der Zeit (Mannheim: Bibliographisches Institut, 1969), pp. 45-50; idem, “Eindeutigkeit, Konsistenz und methodische Ordnung,” in F. Karnbartel and J. Mittelstrass, eds., Zum normativen Fundament der Wissenschaft.
Following the lead of Hugo Dingler, Paul Lorenzen and other members of the so-called Erlangen school have worked out a system of protophysics , which contains all aprioristic presuppositions of empiriical physics, including, apart from geometry, also chronometry and hytometry (i.e., classical mechanics without gravitation, or “rational” mechanics). “Geometry, chronometry and hytometry are a-priori theories which make empirical measurements of space, time and materia ‘possible’.They have to be established before physics in the modern sense of fields of forces, can begin. Therefore, I should like to call these disciplines by a common name: protophysics.” Lorenzen, Normative Logic and Ethics, p. 60.
Great article. I’ve evolved from an empiricist into a rationalist tradition these last few years, in no small part due to the convinving arguments laid out by Mises, Rothbard and, most recently, of Hoppe. Especially after hearing Mises’ strong critique of mathematical and empirical macroeconomics, I became ever more suspicious of what academics were passing off as reasoned argument and “science”.
I think that Popper is fundamentally in error on a number of core issues to do with the scientific method, and rational vs empirical knowledge — although I actually disagree with many of Hoppe’s excellent arguments as to WHY he’s wrong. A few minor points of contention really.
Like many of the philosophers before him, I claim that Popper too misunderstood the difference between two fundamental aspects of human Reason:
* Logical or tautological systems (formal, modal, fuzzy, math, etc) having to do EXCLUSIVELY with artificial or abstract CONCEPTS.
* Rationality (explanations of reality itself), i.e of interacting physical OBJECTS (objects which exist: i.e. shape + location).
Reaility is NOT tautologous. It is just… what it is. We can only rationally explain it; but never “prove” it absolutely (with omniscience). Conversely, ALL logic systems are tautologous.
We merely point at objects and utter a corresponding mouth noise. We do not and cannot “know” reality directly, but only through our subjective senses (which can and do fool us; hence rationality). Science is objective because it is rigorous with definitions and rational (i.e. deals with existing or hypothesized OBJECTS — their mechanics — via explanations… in order to *visualize* so as to understand/communicate).
The current state of tax-funded of science is a circus. Physics has all but been erradicated by mathematicians engaging in Ptolemaic circularity and reification of concepts into objects (scientific fraud, essentially). They believe that time, space, and energy are physical entities (i.e. to do with Physics) rather than just mathematical quantities and abstractions. They continue to propose hyper-dimensions and surrealistic zero-d particles and wave-packets. To this day, not a single phycist on Earth who can even draw any one of the hundreds of particles “predicted” by the standard model of quantum, even thoguh they claim every day to verify them inside reassuringly expensive particle colliders.
Meanwhile the “empirical” state economists and social theorists (also largely hijacked by mathematicians and relativists) engage in similar practices; immoral social and financial “experiments” on a frightening scale.
“Popper would have us throw out any theory that is contradicted by any fact, which, if at all possible, would leave us virtually empty-handed, going nowhere. In recognizing the insoluble connection between theoretical knowledge (language) and actions, rationalism would instead deem such falsificationism, even if possible, as completely irrational. There is no situation conceivable in which it would be reasonable to throw away any theory—conceived of as a cognitive instrument of action—that had been successfully applied in a past situation but proves unsuccessful in a new application—unless one already had a more successful theory at hand.”
Popper’s actual view is that when experimental results contradict our hypothesis, we should consider whether it is advisable to revise our theory. He never suggests we should discard a theory because “any fact” refutes it. His actual view is that we should retain our theory, modified if necessary, unless and until we have a better one to replace it. In addition to being sound reasoning, this is a also a pretty good description of what scientists actually do.