This edition has a superb introduction by Guido Hulsmann, biographer of Mises, explaining the reason why Mises turned to epistemology and why he took it so seriously.
Up to the 1930s it seemed that the Austrian insights were firmly embedded in the mainstream of neoclasical economics, although Wicksell sounded an alarm in correspondence with Marshall when he deplored the drift from Menger's ideas in successive editions of Principles of Economics. Then the calculation debate with the socialists in the 1920s and 1930s, followed by the Keynesian diversion and the rise of positivism in the philosophy of science signalled that there were deep problems and issues in epistemology and methodology that called for further investigation and resolution.
Hayek turned towards the function of dispersed knowledge in society and the "abuse of reason" project, while Mises revisited the major themes and thinkers after the marginal revolution to eliminate some errors from the legacy of Menger, Bohm Bawerk, Weber and others of less note. This book contains a series of papers, most written in the 1920s, on the key areas of value theory and epistemology.
Later, when Human Action fell like a stone in the profession, he concluded that the decisive battleground for the future of economics lay in the basic principles and methods of the discipline. He wrote two more books to sustain his defence of subjectivism and the a priori approach, against historicism and positivism. These are Theory and History (1957) and The Ultimate Foundation of Economic Science (1962).
While Mises was working in Europe, scholars on two other continents were moving along lines that converged with Misian praxeology. In the US Talcott Parsons under the influence of Marshall, Pareto, Durkheim and Weber developed the "action frame of reference" (The Structure of Social Action, 1937) and Karl Popper in Australasia sketched "situational analysis" (The Poverty of Historicism, which appeared as articles in 1943/44 and the book in 1957, also The Open Society and its Enemies 1945 ). That was not the ideal time for collaboration between German and English speaking people and the opportunity for a merging of forces was lost. After The Structure Parsons embarked on general systems theory, inspired by the model of classical mechanics and Popper, engrossed with physics and biology, never engaged fully with the social sciences or the Austrian school, despite his friendship with Hayek.
While Mises is one of the leading economist of the 20th century, his epistemological project has not helped to convince scholars in the mainstream of the strengths of the Austrian program. Maybe the program needs to be made more Austrian by injection of selected ideas from Karl Popper. This has the potential to deliver a nuanced version of methodological monism that does justice to the differences between the natural and the human sciences. The first step is to see how the quest for justified true beliefs (justificationism) has created insoluble problems and misplaced efforts to identify the sources or grounds of such beliefs and the methods required to reveal them. In brief, all attempts to conclusively justify universal propositions lead to an infinite regress.
Methodological dualism is generally based on the assumption that the natural and biological sciences find and justify universal laws by some process (possibly induction), based on observations. In contast the human sciences and the science of human action find and justify their universal laws by some other process of reason or intellectualisation or apprehension of essential tendencies in social systems. Whatever the basis and justification for these laws may be, it is not observation of the external world or sensory experience, as is supposed to be the case for the natural sciencecs.
The Popperian replies that the universal laws of the natural sciences (as we formulate them) are conjectures (more or less freely invented) that have stood up to tests, regardless of their origins which may well be in myths, superstitions and metaphysics. They are not derived from the accumulation of sensory experiences. They are never justified (in the strong sense demanded by justificationists) and they are not tested directly (because they cannot be observed). They are tested (or justified in a weaker sense ) by their capacity to account for observed events, in conjunction with ancillary hypothesis (other laws) and statements of initial conditions. Quite likely the same applies to the universal laws of praxeology which can be used (and tested) to anticipate (or explain in historical retrospect) tendencies (pattern predictions) in the world. Of course the actual laws are quite different in different domains, as are the problems to be solved, the events explained and the observational and experimental technology that is used. Explanations of events in the human sciences will need to take account of another kind of regularity in addition to the universal laws, (and also human plans and intentions), these are institutions and traditions, values, norms and "rules of the game", ranging from local customs to the laws of the land, including the written and unwritten rules of interpretation and application of general principles.
On this account the laws of praxeology do not need to be grounded in the "justificationist" sense, they need to be tested by their capacity to explain events, to provide insight and understanding of processes, to stand up to criticism, to point the way to deeper problems, to integrate different field of study and to generate fruitful research programs. Just like real science!