Theories of Mind (Part 4): The Interaction Problem

Rene Descartes provided a number of arguments for the immateriality of the mind. For that requisite context, check out Part 1Part 2, and Part 3. Today we shall briefly evaluate the principal objection to Cartesianism: the interaction problem. Without further ado, let’s evaluate Descartes’ arguments from dubitability and divisibility.


2.3 The Principal Objection to Descartes’ Substance Dualism

In this section, I outline and motivate the interaction problem as the principal objection to Descartes’ view. Next, I provide a pathway for removing some of the mystery it poses for dualism.

2.3.1 The Interaction Problem

The interaction problem for dualism consists in two seemingly intractable questions concerning the causal influence between mind and body:

(1) How does the mind (body) exert causal influence over the body (mind)?

(2) Where does the mind (body) causally interact with the body (mind)?

The problem seems especially intractable when we consider the radical differences between the two substances posited by Descartes’ theory. The mind, according to Descartes, is utterly unextended, non-spatial, lacks energy, momentum, and mass, lacks size and dimensions, and is wholly immaterial. How on earth could something lacking any spatial dimensions, lacking any energetic influence, and being wholly non-physical causally interact with and act upon something that is essentially spatially extended, energetically influenced, and wholly physical? How could there be any causal contact between these two vastly different realms? The connection seems to be wholly inexplicable.

A difficulty also arises in considering where this supposed interaction is occurring. Is it occuring in the brain? If so, where? And why there as opposed to two picometers to the left or right? And in virtue of what does this unextended substance “latch onto” something that is purely extended? How could it even be meaningful to talk about a dimensionless, unextended thing having a spatial location of its interaction?

These explanatory difficulties, one may argue, provide us with good reason to reject Descartes’ substance dualism.


2.3.2 A Pathway to Remove Some Mystery

To see why the interaction problem is not as mysterious as we might initially think, consider physical causation. What is physical causation? I aver that there is a deep mystery here, a mystery that parallels dualism’s interaction problem.

Just think about it. What is this mysterious relation of “production” whereby one object (event) causes another object (event) to exist (happen)? How does that even occur? We can specify the shapes of the objects, their spatial contiguity, their color, their relative velocities, their kinetic and potential energy, and so on, but where is causality in this specification? In which of these facts does causation consist? To which of these facts could we point?

We say that one billiard ball causes another billiard ball to move. But what is this relation of causation? It won’t do to analyze it in terms of “production”, “power”, “capacity”, or “generation,” since these terms are themselves causal notions and thereby presuppose the very thing to be analyzed. But if we make no reference to such causal notions, instead referring to wholly acausal facts, then it seems we haven’t analyzed causation but rather have eliminated it. For instance, we may analyze causation as constant conjunction, or spatial contiguity, or some other account. But arguably, these accounts merely eliminate causation rather than illuminate its nature. We could analyze physical causation in terms of momentum transfer. But what is momentum transfer? Momentum is a quantity posited to account for conserved quantitative aspects of the causal effects of physical bodies on other physical bodies. If anything, momentum transference either presupposes a causal production of an effect (in which case it is not an illuminating analysis of causation), or it amounts merely to a constant conjunction in which a given quantity is conserved (in which case it seems to eliminate rather than illuminate the causal relation — which is one of the major problems afflicting Humean accounts of causation).

But if physical causation is just as mysterious as non-physical to physical causation, it is unclear what the problem for dualism is. Indeed, arguably causation is primitivea basic, irreducible, unanalyzable metaphysical feature of reality. Indeed, these difficulties in reducing (ontologically or conceptually) the causal relation are precisely what we would expect if the causal relation is primitive.

In fact, there is widespread consensus that causal reductionist theories do not succeed. As two foremost experts on causation point out:

After surveying the literature in some depth, we conclude that, as yet, there is no reasonably successful reduction of the causal relation. And correspondingly, there is no reasonably successful conceptual analysis of a philosophical causal concept. No extant approach seems able to incorporate all of our desiderata for the causal relation, nor to capture the wide range of our causal judgments and applications of our causal concept… The prospects of a relatively simple, elegant and intuitively attractive, unified theory of causation, whether ontological reduction or conceptual analysis, are dim.4

So, it seems we have some reason to be primitivists about causation. But if that is true, then physical-physical causation seems to be every bit as “mysterious” as non-physical-physical causation. Under such an account, both are equally primitive, irreducible, and basic.

A final note in relation to the interaction problem concerns the very nature of how questions. Usually, when we pose a how question, we seek a mechanistic explanation of how one phenomenon gives rise to or interacts with another phenomenon. But, by definition, the immaterial mind is not some mechanistic thing with parts arranged and operating in mechanical ways. But if that is true, then demanding a how explanation in relation to the mind’s activity is (one may argue) a category error.

Author: Joe


Note: References will be contained in the last post of the series.


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