Smith explains how the methodological monism of modern positivism differs from classical empiricism.

George H. Smith was formerly Senior Research Fellow for the Institute for Humane Studies, a lecturer on American History for Cato Summer Seminars, and Executive Editor of Knowledge Products. Smith’s fourth and most recent book, The System of Liberty, was published by Cambridge University Press in 2013.

It was with some reluctance that I began this series on the nature of social “laws,” as found in economics and other human sciences, given the complexity of the topic. But as with all my essays for Lib​er​tar​i​an​ism​.org, I write about what interests me personally, and I have been keenly interested in this controversy for decades. Moreover, since I plan eventually to discuss the social theories of Mises, Hayek, Spencer, and other classical liberal philosophers, I feel it is useful to lay some historical and theoretical groundwork for those future explorations.

Granted, some readers may not be interested in the intricacies of social theory, and others may wonder how such matters relate to libertarianism. To the first group, the uninterested, I have no persuasive reply. I would merely point out that a clear understanding of what we mean when we speak of the “laws” of economics, etc., will enable us to think more clearly about such topics, and that clear thinking is always a good thing. To the second group I would point out that a relationship does indeed exist between libertarianism and social theory, including social theory that extends beyond the boundaries of conventional economics into the broader field of sociology. Ludwig von Mises, for example, argued that no clear line of demarcation separates economics from social theory generally, and that his theory of praxeology (the science of human action) provides a foundation for all the social sciences. Although I disagree with some features of the Misesian approach, I think his basic point is sound.

In my last essay I briefly discussed methodological monism and identified that approach with a school of thought called positivism. This label derives from Auguste Comte’s claim that only “positive knowledge” qualifies as authentic science. And though self‐​styled “positivists” in the nineteenth century typically viewed Comte as their forefather, the term “positivism” was soon embraced by a broader range of thinkers.

Generally speaking, positivists have looked to the physical, or “natural,” sciences (especially physics) for their version of a methodology that should be applied universally to other cognitive disciplines, including the social sciences, history, and philosophy. In this view, the natural sciences owe their spectacular progress to their reliance on empirical verification, having repudiated a priori speculation and appeals to unobservable metaphysical essences. If the human sciences have failed to keep pace with the natural sciences, this is principally because the former have not fully adopted the strict empirical methodology of the latter.

Empiricism – by which I mean the classical empiricism of the seventeenth and eighteenth centuries – is sometimes portrayed as a forerunner to modern positivism, but this is a misleading characterization. Positivism may be viewed either as an improvement of classical empiricism or as a degeneration, depending on our theoretical proclivities. Defenders of positivism might claim that classical empiricism was a latent form of positivism which, having shed its undesirable features in the nineteenth century, eventually blossomed into an approach that was truly scientific. Contrariwise, critics might claim that positivism was an aberration of classical empiricism, one that tragically ignored or excluded some of empiricism’s most important insights.

Classical empiricism, as pioneered by Francis Bacon and John Locke, was based on the premise that all knowledge is ultimately derived from experience, whereas positivism claims that scientific knowledge must be capable of being verified through sense perception. Empiricism is a theory about the origin of knowledge, whereas positivism is a theory about the justification of scientific knowledge – and the latter does not necessarily follow from the former. Let’s glance at two significant differences between classical empiricism and modern positivism.

(1) Many classical empiricists did not embrace the methodological monism that would become the keystone of positivism. Consider this typical statement by a luminary of the French Enlightenment, the mathematician and philosophe Jean d’Alembert:

If one reflects somewhat upon the connection that discoveries have with one another, it is readily apparent that the sciences and the arts are mutually supporting, and that consequently there is a chain that binds them together. But, if it is often difficult to reduce each particular science or art to a small number of rules or general notions, it is no less difficult to encompass the infinitely varied branches of human knowledge into a truly unified system. (Preliminary Discourse to the Encyclopedia of Diderot, 1751, trans. Richard N. Schwab, Bobbs‐​Merrill, 1963, p. 5.)

The unification of the sciences, as envisioned by many Enlightenment philosophers, was to be achieved through an understanding of epistemology. All knowledge, whatever its source and method of verification may be, is human knowledge. Thus only if we understand how our ideas originate and how they are formed can we discern what the sciences have in common and how they are related. Again quoting d’Alembert:

The first step which lies before us in our endeavor is to examine, if we may be permitted to use this term, the genealogy and the filiation of ideas of the parts of our knowledge, the causes that brought the various branches of our knowledge into being, and the characteristics that distinguish them. In short, we must go back to the origin and generation of our ideas. (Preliminary Discourse, p. 5.)

When seventeenth‐ and eighteenth‐​century empiricists defended a universal method, one that enabled them to place every field of inquiry within the same system of knowledge, they were usually thinking of epistemology, not the scientific method per se. They were thinking of a common philosophical foundation on which all the sciences could be based. This approach differs considerably from the methodological monism that we find in modern positivism.

Ever since Descartes presented the “clear and distinct” ideas of mathematics as the criterion of certain knowledge, various philosophers and scientists have vied over which science should serve as the exemplar for the rest. The model of geometry, which dominated seventeenth‐​century rationalism, gave way (more or less) to the model of Newtonian physics, which dominated eighteenth‐​century empiricism. But, as we shall see, the adoption of the Newtonian method did not necessarily lead eighteenth‐​century empiricists into a crude form of positivism, as has sometimes been the case with those modern philosophers who have upheld physics as the exemplar of the scientific method.

Many early empiricists understood a crucial point that many modern positivists do not – namely, that the method of a particular science will yield general insights and will be applicable to other sciences only when that method has been related to, and explained in terms of, a more fundamental theory of knowledge. The Newtonian method was widely admired, not merely because it had produced spectacular results in celestial mechanics and optics, but also because it seemed to illustrate and expand upon the empiricist theory of knowledge, especially as defended by John Locke.

The classical empiricists did not extract their method from Newtonian physics and then apply it wholesale and without alteration to the human sciences. They did not pound the square peg of the human sciences into the round hole of the Newtonian method, as employed in physics, dismissing whatever would not fit as unscientific or as useless metaphysical speculation. Instead, they examined the broader epistemological implications of the Newtonian method and then adapted it to the specific nature and cognitive needs of the human sciences. Contrary to modern positivism, the classical empiricists did not transfer a successful method from one science (physics) directly to the other sciences. Rather, they took an all‐​important detour through epistemology, moving from physics down to the foundation of all knowledge, and then back up again to the human sciences. Physics was for them one example, not a universal exemplar, of correct methodology. Just as Newton had succeeded by adapting the principles of empiricism to fit his particular needs, so others could adapt the same epistemological principles to fulfill the cognitive needs of their respective sciences.

(2) Lockean empiricists, while insisting that all knowledge is rooted in experience, did not confine experience to our perceptual contact with the external world. On the contrary, Locke divided experience into two categories, sensation and reflection, and he regarded these as equally important wellsprings of knowledge.

Sensation, which is generated by the interaction between our physical senses and the external world, is the source of our knowledge about concrete objects and attributes. Reflection, in contrast, consists of directing our attention inward, within our own minds and bodies, in an effort to isolate and identify our inner processes, feelings, and states of mind, both cognitive and psychological.

There is within classical empiricism no methodological prejudice that favors external perception over internal reflection, as if the former were somehow a more reliable process than the latter. But this is a prejudice that runs deep within positivism; it exists to some degree in each of its forms (as a presumption at least, if not as an explicit rule). For instance, Auguste Comte expressed contempt for the introspective procedures of psychology and economics because their claims supposedly could never be verified by legitimate scientific means. If philosophy and the human sciences wish to attain the status of authentic sciences, they must follow the example set by the physical sciences. They must eschew all theories based on subjective introspection and confine themselves to claims that can be verified through external observations and experiments.

As I noted earlier, this call for empirical verification without recourse to introspection should not be confused with the agenda of classical empiricism, even though both traditions sometimes employed similar language. Introspection, for many classical empiricists, was indispensable not only for the human sciences but also for mathematics, history, and the natural sciences (or “natural philosophy,” to use an earlier label). This point is illustrated in David Hume’s remark that mathematics, natural philosophy, and even natural religion “are in some measure dependent on the science of Man; since they lie under the cognizance of men, and are judged of by their powers and faculties.”