The free energy principle free energy principle (FEP) is ambitiously touted as a unified theory of the mind, which should be able to explain everything about our mental states and processes. Dominic L. Harkness discusses the route from the principle to actual explanations. He reasonably argues that it is not immediately obvious how explanations of actual phenomena can be extracted from the free energy principle, and then offers positive suggestions for understanding FEP’s potential for fostering explanations. The argument I focus on in Hohwy (this collection) is that FEP is not so preposterous that it cannot explain at all; Harkness’s commentary thus raises the important point that there may be other obstacles to explanatoriness than being preposterous.
A further aspect of Harkness’ approach is to make contact between the discussion of FEP’s explanatory prowess and discussions in philosophy of neuroscience about computational and mechanistic explanation. This matters, since, if FEP is really set to dominate the sciences of the mind and the brain, then we need to understand it from the point of view of philosophy of science.
In this response, I will attempt to blur some distinctions between notions currently discussed in the philosophy of science. This serves to show that there is a diversity of ways in which a theory, such as FEP, can be explanatory. I am not, however, advocating explanatory pluralism; rather, I am roughly sketching a unitary Bayesian account of explanation according to which good explanation requires balancing the diverse ways in which evidence is explained away. This seems to me an attractive approach to scientific explanation—not least because it involves applying FEP to itself. The upshot is that even though FEP is not yet a full explanation of the mind, there are several ways in which it already now has impressive explanatory prowess.