Hume's Fork and Psychiatry's Explanations: Determinism and the Dimensions of Freedom

August 1, 2007

An item in the Boston Globe recently caught my eye. Apparently, a man who was fired by a large corporation for visiting an adult "chat room" while at work is suing the company. The man is claiming he is an "Internet addict" who "deserves treatment and sympathy rather than dismissal." Another item reported recently concerned a lawyer who argued that her client was not responsible for a rampage that he had committed because he "had been obsessed with comic book superheroes as a kid."

These items piqued my interest not merely because they play into the public's worst stereotypes concerning psychiatric diagnosis-"You shrinks think every kind of bad behavior is a disease!"-but also because they raise the most fundamental questions concerning freedom, responsibility, and mental illness. Since the vexing question of "free will" has been debated by theologians and philosophers for centuries, with neuroscientists weighing in more recently, I do not propose to resolve this matter in the space of one column (even medical editors are not that grandiose). I do hope to present an overview of the philosophical issues as they impinge on psychiatric theory and practice, and to put forward a conceptual schema for understanding how persons may have a mental illness and yet be responsible in some measure for their actions.

However, to accomplish the latter, I first need to put forth a somewhat unfamiliar, if not unwelcome, concept of what it means to act using free will. Informulating my position, I am indebted to the work of philosophers Moritz Schlick, Thomas W. Clark,3 Owen Flanagan,4 and Daniel C. Dennett,5 among many others.

Stuck by Hume's fork

Let's begin by considering a paradox known in philosophical circles as "Hume's fork," ostensibly derived from the work of the great Scottish philosopher David Hume.6 The paradox goes something like this: Either all our actions are determined, in which case we are not responsible for them; or, our actions are the result of random events, in which case we are still not responsible for them!

To understand the first part of this dilemma, we briefly need to consider the concept of determinism. In its most basic formulation, determinism simply asserts that everything that happens is caused, and that when an event occurs, nothing other than that event could have occurred at that particular moment given precisely the same conditions immediately preceding the event. Determinism is not to be confused with fatalism or predestination, both of which imply that no matter what we do, the future will turn out in one and only one way. Determinism asserts, on the contrary, that our actions are crucial in shaping the future.

Keeping this in mind, we can see that the first part of Hume's dilemma might imply nothing less than this: If all our wishes, desires, and actions are merely the inevitable result of innumerable causal factors coalescing since the beginning of time, we cannot possibly have free will or reasonably be held morally accountable for our actions. (Thomas Aquinas appreciated these implications more than 7 centuries ago.)

You can easily imagine how this argument, applied to the subset of persons who have serious psychiatric disorders, becomes even more destructive to our commonly held notions regarding freedom and responsibility. If everyone's actions are merely the result of a chain of causation extending back ad infinitum, how much less free will must someone with schizophrenia have? He or she, after all, carries the added "causal burden" of brain pathology based on the best available science. And how could we possibly argue that such brain-impaired persons should be held accountable in any way for their actions? With this view, surely, our "Internet addict" (whatever that means) might just have a case in denying any culpability for his on-the-job behavior.

And alas, the other "tine" in Hume's fork does not help us much either if we are intent on salvaging our ordinary concept of personal responsibility. If our actions do not proceed from an unbroken chain of causal events; if, on the contrary, our behavior is the product of random factors operating beyond the realm of causality, then we are clearly not the authors of our actions in any meaningful sense. By the way, the quantum mechanics loophole-the hypothesis that strict determinism may not hold at the level of subatomic particles-does not do us much good, because the molecular and electrochemical events in the brain occur on a scale many magnitudes larger than that of Heisenberg's wave-particle uncertainty principle.

Bending Hume's fork

Philosophers, ethicists, and theologians have proposed several ways out of Hume's dilemma, and it is beyond the scope of this brief piece to review them.4,6,7 However, I would like to defend the position taken prominently by the German philosopher Moritz Schlick that determinism and causal law do not vitiate free will or moral responsibility. On the contrary, Schlick argued that our ability to act with genuine freedom depends on causality and determinism.7 Schlick pointed out that causal laws are not proscriptive in the way that civil laws are; rather, they are descriptive and merely tell us how the physical world actually functions. The view that determinism and free will are compatible is sometimes termed "compatibilism" or, in more recent versions, "neo-compatibilism."4 Of course, Schlick's position rests on the admittedly controversial hypothesis that determinism invariably operates throughout the universe-and thus, in the sphere of our own thoughts, feelings, and actions.

Essentially, the compatibilist argument is that we cannot be free or responsible beings if our actions are mysteriously chosen by an entity that somehow slips the surly bonds of causal law and acts independently of our goals, values, and wishes. On the contrary, whether we call that volitional entity "will," "soul," "psyche," or "I," it must be causally linked with our core values to effect morally responsible actions. That is, to preserve free will, the "state of my will (itself determined by prior and contemporaneous causes) must be a sufficient cause of any choice I make."4

Indeed, I would like to suggest that the tighter the causal links between our decision-making capacity and our innermost values, the freer and more responsible are the decisions that we make.

Degrees of freedom

Notwithstanding the compatibility of freedom and determinism (in my view), freedom is not an either/or condition. Rather, actions may be more or less free, and more or less responsible, depending on a number of contingent factors. There are, in short, degrees of freedom. Psychiatrists can be most helpful insofar as we can describe, study, and categorize these degrees of freedom and the psychopathological conditions that so tragically undermine them. (This last point was poignantly driven home by the recent shootings at Virginia Tech.)

And yet, while I do not believe that the notion of an "autonomous self" free of causal law (contracausal free will) can be scientifically defended, I do not want to jettison the concept of the autonomous self. Indeed, with proper conceptual rehabilitation, the concept still has what philosopher William James might have called "cash value"; it can still do useful philosophical "work" for us if understood properly. (As the pragmatic James famously put it, "Theories thus become instruments, not answers to enigmas."8)

To appreciate all this, let's begin with a thought experiment. Imagine that some nefarious inventor has contrived a device called the assault machine (AM). This evil machine is attached to a person's arm, rather like a blood pressure cuff, and has an electrode that penetrates the substance of the brain. The AM has a visual recognition component that activates its motor apparatus-the purpose of which is to "whack" the nearest person within one's reach! The AM has the ability to override the person's higher brain centers, such that he is absolutely powerless to resist carrying out the assault. Let's now suppose that Jones is hooked up to the AM, quite against his will. Smith happens to walk by Jones and, as expected, Jones (well, his arm at least!) whacks Smith in the head. Now, in my view, the AM provides what my old Cornell philosophy professor Max Black9 used to call a "perfectly clear case" in which free will and agential action are essentially in-operative, based on what Black would call our "ordinary language." That is, Jones' assault on Smith was not causally related to the hopes, wishes, goals, and rational purposes unique to Jones; rather, the proximal cause of the assault was the action of the nefarious device.

How is this thought experiment related to the concept of the autonomous self? Essentially, the AM vitiates our ordinary language understanding of the autonomous self. To appreciate this, let's consider another vignette on the opposite side of the continuum that is being developed here.

Our friend Jones-having been acquitted of any criminal charges in the Smith assault incident-now returns to his home, where he is enjoying his hobby of painting. He stands, brush in hand, deliberating as to what he will now paint, in what style (eg, abstract expressionism, realism, etc), and with what colors. Jones has not been externally constrained, so far as we know, in any way; he has not been commissioned to produce one particular kind of painting; and he has no limits as to available art supplies, choice of paint, etc. Again, I would argue that this is a perfectly clear case in which the autonomous self and agential action-action taken by a rational and deliberative person-are essentially preserved. Now, this is surely not to argue that any of Jones' artistic decisions are somehow uncaused or supernaturally liberated from the laws of physics and neurochemistry! Jones' actions are, to be sure, mediated by his brain-and his brain is a physical entity constrained by physical laws. Yet, in our ordinary language, I believe we would consider Jones to be acting freely-using free will. We would also say, in my view, that Jones, as artist, is now responsible for his actions in a very robust sense.

Before relating all this to psychiatric disorders, let's consider, finally, a middle case. Let's suppose that it is the year 2025 and neuroscientists have isolated a neuropeptide dubbed "assaultin." Assaultin, it turns out, is coded for by the gene "BAD2U." Behavioral scientists have established, in 32 randomized controlled studies, that when this neuropeptide is injected into the cerebrospinal fluid of human subjects, 65% become immediately and dramatically assaultive. Ah-but 35% of them do not become assaultive. Indeed, psychological studies of these nonassaultive subjects reveal that nearly all employ a certain cognitive strategy to overcome the powerful impulse to become assaultive-they repeat a sort of mantra that helps them retain self-control.

Moreover, when the 65% of subjects who do become assaultive are taught this marvelous mantra, 50% are able to resist the effects of subsequent assaultin injections. The key question is where on the "degrees of freedom" continuum would we place the brain state associated with "assaultin injection" in relation to (a) the condition of having the assault machine strapped to the arm (Jones, case 1) and (b) the condition of being left alone with one's paints and canvas (Jones, case 2)? I would argue that we would place the neuropeptide-induced brain state somewhere between the other 2 instances-probably closer to Jones, case 1 than to Jones, case 2.


If this heuristic model has any utility in psychiatry, we ought to be able to place a variety of brain states and psychiatric disorders somewhere along the degrees of freedom continuum. (I am assuming here that psychiatric disorders are essentially highly complex, aberrant brain states.) I have suggested a few purely speculative placements in the Figure. The actual placement of brain states and putative disorders would depend crucially on the empirical evidence gathered in understanding these conditions; for example, to what degree does a person who has schizophrenia have the ability to resist obeying so-called command hallucinations to harm someone? The answer undoubtedly differs from patient to patient-depending on a multitude of genetic, biochemical, and psychological factors. (The term "psychological" is not intended to imply something nonmaterial; rather, it is shorthand for brain processes that we experience and express in terms of motivations, wishes, understandings, fears, etc.)

In part 2 of this editorial, I will elaborate on the "naturalistic" model of freedom and autonomy and suggest how it may be applied to psychiatric disorders and medico-legal determinations of culpability.




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Blume H. Q & A: Jonathan Lethem.

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Clark TW. Applied ethics: science and freedom. Council for Secular Humanism Web site. Available at: library&page=clark_22_2

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