It’s the spirit of the Scottish Enlightenment that’s closest to the spirit of my work. Francis Hutcheson (1694-1746) was one of the founding fathers of the Scottish Enlightenment, and soon after Hutcheson came several giants, David Hume (1711-1776) the greatest among them.

In the 19th century, though, Alexander Bain (1818-1903) was one of the most important of the Scots still working as part of the tradition of the Scottish Enlightenment, and (according to The Stanford Encyclopedia of Philosophy here) Bain stood on the cusp: He argued for the replacement of “the philosophy of mind” with “empirical psychology,” which in doing so he helped bring about—though of course the zeitgeist of the 19th century surely made that transition inevitable. In short: The kind of thinking that Hutcheson, Hume, and others did was no longer considered to shed light on metaphysics (i.e., on questions about the ultimate fundamentals of reality). It was demoted to being about the mind and the mind only. It became nothing more than the systematic introspection into the system of the mind, with the mind taken in that new paradigm as a thing apart from reality.

The killing blow, then, to the weakened tradition of the Scottish Enlightenment, was the tabooing of introspection. The “philosophy of mind” (the term “philosophy” at that time being equivalent to the term “science” nowadays) became “empirical psychology,” and then in turn what was admitted as “empirical” eventually shifted: The mind was no longer admitted as a proper object of empirical observation. In psychology, from then on, only models of the brain (along with anything else physical, e.g. the eye, the ear) were taken as properly scientific.

In summary: The “philosophy of mind” in the 18th century became a kind of “empirical psychology” founded on introspection in the early 19th century, which in turn became a different kind of “empirical psychology” by the late 19th century. The analysis of the mental mechanisms of human action and the human mind was pushed aside, and the analysis of the physical mechanisms thereof took over.

With all of that said, however: I’d like to argue that, actually, the tradition of the Scottish Enlightenment didn’t just degenerate first into introspective psychology (with Bain) and then into non-introspective psychology (post-Bain); it actually split off at the root, growing not only into psychology, on one hand, but also logic, on the other hand. Hume introspected in order to understand (the fundamentals of) the system of the mind in its understanding of (the fundamentals of) the system of reality. Post-Bain, the new field of psychology specialized in the former part of that, viz. in the goal of understanding the mind in a fundamental and systematic way, and the new field of logic specialized in the latter part of that, viz. in the reality-related considerations. And mirroring the further degeneration into non-introspective psychology, logic too degenerated: It lost its substance as it transformed into formal logic. John Stuart Mill’s treatise A System of Logic (1843), which Mill thought of as a contribution to the “science of science itself,” soon went out of fashion—it was almost entirely prose. Boole in The Laws of Thought (1854) adapted algebraic notation to logic, and from then on it was formal (or mathematical) logic that inspired the intellectual world—a project that (to no fault of Boole’s) became increasingly unmoored from the Scottish tradition (along with the broader British tradition, e.g. in Locke, in Berkeley) of checking whether there’s actual substance underneath the pretty surface form of eloquent words and other symbols.

And finally, in the 21st century: Introspection is taboo in science, the physical is taken much more seriously than the mental in psychology and elsewhere (in keeping with introspection as taboo in science), a substance-unchecked mathematics has all but swallowed up logic, and there are few thinkers left in philosophy of science.