Physicist Sean Carroll, an outspoken but ever-courteous defender of the New Atheism, has recently written a post entitled, The Case for Naturalism, at the end of which he kindly encloses a 10-minute video summary of the reasons which have led most scientists to reject the supernatural and accept that the natural world is all there is. The video, which is well worth watching, is excerpted from a two-hour debate held at Caltech on 27 March 2012, on the topic, Has Science Refuted Religion?. Sean Carroll and Michael Shermer argued for the affirmative, while Dinesh D’Souza and Ian Hutchinson argued for the negative.
In the course of his video presentation, Professor Carroll makes reference to a most remarkable woman from the seventeenth century: Princess Elisabeth of Bohemia (1618-1680), who corresponded with the philosopher Rene Descartes on various philosophical matters. Princess Elisabeth was a very learned woman who spoke six languages, was talented at mathematics and was also a gifted painter.
What, you might wonder, does a 17th century princess have to do with the case for naturalism? As Sean Carroll explains in his video, Princess Elisabeth‘s gentle probing of Descartes’ dualism exposed a key weakness in his philosophy – namely, that he was unable to explain how the mind and body interact:
“It’s very natural, very commonsensical to think that a living person possesses something that a corpse does not – some sort of spirit, some sort of animating soul of life force, But this idea, as it turns out, does not stand up to closer scrutiny. And a big step towards realizing this was made back in the 1600s by a remarkable woman named Princess Elisabeth of Bohemia. They named princesses differently back in the 17th century! Elisabeth carried on a years-long correspondence with Rene Descartes who famously tried to develop a theory of mind-body dualism. And Elisabeth said, “I don’t understand what you’re saying, because if you really believe that the mind is in a separate realm from the body, my mind makes a choice to lift my arm, but it’s my body that does it. How does the immaterial mind, which as you say doesn’t exist at a location in space, how does it act causally on the body? How does it interact with the stuff out of which you were made?” And Descartes never came up with a reliable, believable response to this objection. Of course these days the objection is enormously stronger. We’d say: “You are made of atoms. You’re made of cells which are made of molecules which are made of atoms, and as physicists, we know how atoms behave. The laws of physics governing the behavior of atoms are completely understood. You put an atom in a certain set of circumstances, and you tell me what those circumstances are, as a physicist I will tell you what those atoms will do. If you believe that the atoms which are inside your body act differently than they would if they were inside a rock or a crystal, then what you’re saying is that the laws of physics are wrong, that they need to be altered because of the influence of a spirit or soul. That may be true, science can’t disprove that, but there is no evidence for it.” (Emphases mine – VJT.)
Professor Carroll’s historical narrative is correct so far as it goes, but there is a lot that he leaves out. To begin with, Princess Elisabeth wasn’t a religious skeptic. Professor Carroll never says she was, of course, but a casual viewer of his video might walk away with that impression. In fact, Princess Elisabeth was a devout Protestant, who (in 1667) became abbess of a Lutheran Abbey at Herford, Saxony, where (according to her Wikipedia biography) “she distinguished herself by faithfulness in the performance of her duties, by her modesty and philanthropy, and especially by her kind hospitality to all who were oppressed for the sake of conscience.” For his part, Rene Descartes was a Catholic, whose philosophical views were highly unconventional for his day, but whose deep religious faith prompted the Lutheran Queen Christina of Sweden to renounce her throne in order to convert to the religion of her personal tutor, after Descartes’ death in 1650.
The key point here is that in their philosophical correspondence, both Princess Elisabeth and the philosopher Rene Descartes shared a firm belief in the reality of the soul, which Professor Carroll derides as an idea which “does not stand up to closer scrutiny.” What, then, was the source of their disagreement?
Philosopher Deborah Tollefsen addresses this question in an article in Hypatia (14.3, 1999, pp. 59-77), entitled, Princess Elisabeth and the Problem of Mind-Body Interaction. As Tollefsen explains, the disagreement between Princess Elisabeth and Descartes boiled down to the fact that Descartes was a very radical, thoroughgoing dualist who defined the soul in terms of a single property – thought – while defining bodies in terms of another fundamental property: extension. As Princess Elisabeth sensibly pointed out, the total disparity in the properties of the body and the soul makes it impossible to conceive of how the two might interact. (Other critics of Descartes’ had also highlighted this glaring weakness in his radical version of dualism, as Tollefsen mentions in her article.) So what was Princess Elisabeth’s solution? She suggested that in addition to the property of thought, the soul might also have spatial properties, making it physically extended in some fashion. As she put it in a letter to Descartes:
I too find that the senses show me that the soul moves the body; but they fail to teach me (any more than the understanding and the imagination) the manner in which she does it. And, in regard to that, I think there are unknown properties in the soul that might suffice to reverse what your metaphysical meditations, with such good reasons, persuaded me concerning her inextension. And this doubt seems founded upon the rule you lay down there in speaking of the true and the false–namely, that all our errors occur from forming judgements about what we do not sufficiently perceive. Although extension is not necessary to thought, yet not being contradictory to it, it will be able to belong to some other function of the soul (no) less essential to her.
(Blom, John. 1978. Descartes, his moral philosophy and psychology. New York: New York University Press, p. 117; Descartes 1972. Oeuvres de Descartes. Vol. 4. Ed. Charles Adams and Paul Tannery. Paris: Librarie Philosophique J. VRIN, 4:2.) (Emphases mine – VJT.)
Tollefsen helpfully elucidates the Princess’s thinking on this issue:
Elisabeth is unhappy with Descartes’s definition of the soul; she pushes him to consider its other attributes because she is convinced that to explain the interaction between mind and body the soul must have an extended element…
Recall that in Elisabeth’s first letter to Descartes she asks him to consider the other attributes of the soul. Here she has returned to this idea. There may be an attribute of the soul, no less essential, which is extended and this extension explains how the soul can move the body and how the body can move the soul. Descartes does not respond to this suggestion. Given his view that the soul has only one essential attribute, he probably found Elisabeth’s suggestion unacceptable. The correspondence shifts at this point from the topic of mind-body interaction to Elisabeth’s health and from there to discussions of moral goodness, the passions, and free will. No mention of Elisabeth’s suggestion occurs in the rest of the correspondence. Although the suggestion that the soul is extended is not one which Descartes’s metaphysics could embrace, it should be noted that this was a common view at the time. (1999, pp. 73, 72. Emphases mine – VJT.)
The Achilles’ heel of Descartes’ radical version of dualism was he defined soul and body in such a way as to make them so disparate in their properties that they could never conceivably interact. Why, then, does Professor Carroll overlook alternative versions of dualism which are far more sensible, and not vulnerable to the same difficulties? At this point, Carroll might reply that Descartes, for all his faults, was at least perfectly clear about what he was proposing, while Princess Elisabeth’s proposed alternative is somewhat vague. It is no use saying that the soul has spatial properties unless you tie them in with its other properties, in a coherent fashion. Besides, the notion of an immaterial thing having spatial properties sounds very mysterious.
Another solution: hylemorphic dualism
It would have been helpful if Professor Carroll had examined a far older dualistic philosophy than Descartes’, which claimed to be able to explain the interaction of soul and body in a smooth, seamless fashion: hylemorphic dualism, which was also espoused by Aquinas and other medieval Scholastic philosophers. Unfortunately, in the 17th century, it had fallen out of vogue in many quarters, but it still has its doughty defenders, to this day. One of the most lucid and articulate of these is Edward Feser, Assistant Professor of Philosophy at Pasadena City College, California. It so happens that Professor Feser has addressed the very problem that plagued Descartes in a blog post entitled, The interaction problem. As Feser sees it, the key problem with Descartes’ dualism was that he conceived of the union of soul and body in purely mechanical terms:
Aristotle and the Scholastic tradition influenced by him famously held that to understand a thing required knowing each of its four causes: its material cause, the stuff out of which it is made; its formal cause, the specific form or essence that stuff has taken on, and which makes it the kind of thing it is; its efficient cause, that which brought it into existence; and its final cause, the end or purpose toward which it is directed. Modern thought is largely defined by its rejection of two of Aristotle’s four causes. For the moderns, there are no such things as substantial forms or fixed essences, and there are no ends or purposes in nature. There are just brute material elements related by purposeless, meaningless, mechanical chains of cause and effect.
As I have emphasized in my series of posts on dualism, this “mechanical” conception of nature, insofar as it stripped matter of anything smacking of either goal-directedness or sensible qualities as common sense understands them, and relocated these features into the mind, more or less automatically entailed a Cartesian form of dualism on which intentionality and qualia are immaterial as a matter of conceptual necessity. But it also automatically entailed that this form of dualism would suffer from the notorious “interaction problem.”
One problem with Descartes’ version of dualism, then, is that he was working with an emaciated concept of matter. Matter, as he envisaged it, had no built-in dispositions or tendencies: its essence consisted in the simple property of extension. Causal interactions between material objects were regarded in mechanical terms. In Feser’s words:
For the moderns, all causation gets reduced to what the Aristotelians called efficient causation; that is to say, for A to have a causal influence on B is for A either to bring B into being or at least in some way to bring into existence some modification of B. Final causality is ruled out; hence there is no place in modern thought for the idea that B might play an explanatory role relative to A insofar as generating B is the end or goal toward which A is directed.
The notion of form, which was so central to Scholastic philosophy, was also shunted to one side:
Formal causality is also ruled out; there is no question for the moderns of a material object’s being (partially) explained by reference to the substantial form it instantiates. We are supposed instead to make reference only to patterns of efficient causal relations holding between basic material elements (atoms, or corpuscles, or quarks, or whatever).
Thus, if the mind considered as immaterial is to have any explanatory role with respect to bodily behavior, this can only be by way of some pattern of efficient causal relations – to put it crudely, in terms of a Cartesian immaterial substance (or perhaps various immaterial properties) “banging” into the material substance (or material properties) of the brain like the proverbial billiard ball. How exactly this is supposed to work is notoriously difficult to explain.
How, then, does hylemorphic dualism solve the interaction? Professor Feser argues that the interaction problem disappears when we treat the soul as the form of the body and not as a separate thing. On this model, the problem of how the soul can interact with the body simply never arises:
But from an Aristotelian-Scholastic point of view, this whole [Cartesian] picture of the mind-body relationship is hopelessly wrongheaded from start to finish. It is wrong to think of the soul (of which the intellect is for Aristotelians but a part, not the whole) and the body as independent objects in the first place. The soul is rather a form that informs the matter of the body and the body is the matter which is informed. As with the form and matter of a stone, tree, or earthworm, what we have here are not two substances interacting via efficient causation, but rather two metaphysical components of one substance related by formal causation. As the form of the stone is to the matter making up the stone, the form of the tree to the matter making up the tree, and the form of the earthworm to the matter that makes up the earthworm, so too is the human soul to the human body. There is in principle no such thing as the matter of a stone, tree, or earthworm apart from the form of a stone, tree, or earthworm respectively, and no such thing as the form of any of these things existing apart from their matter. The form and matter don’t “interact” as if they were two distinct objects; rather, the form constitutes the matter as the (one) kind of object it is in the first place.
My soul, then, is what makes my body a human body, and not the body of a chimp or some other organism, or a pile of dust. Whenever I act, my actions have a final cause (the end I’m trying to achieve), a formal cause (the pattern or structure of the action itself), a material cause (the matter in my body that actually carries out the action) and an efficient cause (whatever it is that makes my body move when I act). Professor Feser contends that when I perform a bodily action such as writing a blog, the movement of neurons in my brain and arm and the attendant flexing of muscles constitute the material cause of my action, and also the efficient cause, presumably because these neurons are the parts of my body whose movements cause my hands to move when I press the keys on my computer. My thoughts and intentions, on the other hand, comprise the formal cause and the final cause of my action: my thoughts give the blog post the “form” or structure that it has as an essay, while my intentions define my purpose for writing the post. In Feser’s own words:
As I move my fingers across the keyboard, then, what is occurring is not the transfer of energy (or whatever) from some Cartesian immaterial substance to a material one (my brain), which sets up a series of neural events that are from that point on “on their own” as it were, with no further action required of the soul. There is just one substance, namely me, though a substance the understanding of which requires taking note of each of its formal-, material-, final- and efficient-causal aspects. To be sure, my action counts as writing a blog post rather than (say) undergoing a muscular spasm in part because of the specific pattern of neural events, muscular contractions, and so forth underlying it. But only in part. Yet that does not mean that there is an entirely separate set of events occurring in a separate substance that somehow influences, from outside as it were, the goings on in the body. Rather, the neuromuscular processes are by themselves only the material-cum-efficient causal aspect of a single event of which my thoughts and intentions are the formal-cum-final causal aspect.
Here, then, we have a version of dualism which claims to be immune to the problems that beset Descartes. It is this older version of dualism, known as hylemorphic dualism, that was propounded by the medieval Church, and that continued to be promulgated (albeit in a somewhat watered-down form) by many Christian philosophers, even in the 17th century. Professor Carroll’s picture of religion as retreating before the relentless march of scientific naturalism is simply at odds with the facts. It is a great pity that he never attempted to critique this version of dualism in his opening statement at the “Great Debate” held at Caltech on March 27, 2012.
Problem solved? Not quite
It would be tempting at this point to declare the case closed. But an outstanding problem remains. The problem, as I see it, is that Professor Feser does not address the question: what is the efficient cause of the movement of neurons in my brain, when I am writing a blog? What makes these neurons move? What pushes them? An obvious answer would be “the soul,” but Feser expressly rules this out:
The soul doesn’t “interact” with the body considered as an independently existing object, but rather constitutes the matter of the human body as a human body in the first place, as its formal (as opposed to efficient) cause.
There are two comments that I would like to make here. The first is that Professor Feser’s remarks address only a crude Cartesian form of dualism, according to which the soul is nothing more than the efficient cause of movement in the body (which is ontologically distinct from it). In other words, the soul is not the body’s form but simply its motor. (This is the standard reading of Descartes’s views, although some scholars interpret him differently.) However, Feser seems to overlook another possibility: that the soul is indeed the form of the body (as hylemorphic dualists maintain), but that it is also able to act independently of the body’s matter, and cause certain parts of the body (e.g. neurons in the brain) to move. Here, the soul would be acting as an efficient cause as well as a formal cause.
Second, Feser’s solution to the interaction problem ignores the question of whether the cause of the movement of neurons in my brain is a deterministic cause or not. For instance, if outside stimuli impinging on my body cause the neurons in my brain to move, then it seems there is no room for human freedom, as the action of these stimuli can be described in a deterministic fashion on a molecular level. Throwing in a bit of indeterminism at the subatomic level doesn’t seem to help matters, either; it just creates an element of randomness, which is not the same thing as freedom.
Freedom: it’s not as difficult as you might think
So how is libertarian freedom possible? The answer, I believe, lies in the notion of in top-down causation. To see how this might work, suppose that my brain performs the high-level act of making a choice, and that this act imposes a constraint on the quantum micro-states of tiny particles in my brain. This doesn’t violate quantum randomness, because a selection can be non-random at the macro level, but random at the micro level. The following two rows of digits will serve to illustrate my point.
1 0 0 0 1 1 1 1 0 0 0 1 0 1 0 0 1 1
0 0 1 0 0 0 0 1 1 0 1 1 0 1 1 1 0 1
The above two rows of digits were created by a random number generator. The digits in some of these columns add up to 0; some add up to 1; and some add up to 2.
Now suppose that I impose the non-random macro requirement: keep the columns whose sum equals 1, and discard the rest. I now have:
1 0 1 1 1 0 0 0 0 0 1
0 1 0 0 0 1 1 0 1 1 0
Each row is still random (at the micro level), but I have now imposed a non-random macro-level constraint on the system as a whole (at the macro level). That, I would suggest, is what happens when I make a choice.
Notice that nothing in the foregoing account requires a violation of energy conservation, or of the laws of physics. Following the philosopher Elizabeth Anscombe, I would maintain that these laws, like the rules of a chess game, constrain but do not determine our bodily movements – and the neural processes that generate them.
Top-down causation and free will
What I am proposing, in brief, is that top-down (macro->micro) causation is real and fundamental (i.e. irreducible to lower-level acts). For if causation is always bottom-up (micro->macro) and never top-down, or alternatively, if top-down causation is real, but only happens because it has already been determined by some preceding occurrence of bottom-up causation, then our actions are simply the product of our body chemistry – in which case they are not free, since they are determined by external circumstances which lie beyond our control. But if top-down causation is real and fundamental, then a person’s free choices, which are macroscopic events that occur in the brain at the highest level, can constrain events in the brain occurring at a lower, sub-microscopic level, and these constraints then can give rise to neuro-muscular movements, which occur in accordance with that person’s will. (For instance, in the case I discussed above, relating to rows of ones and zeroes, the requirement that the columns must add up to 1 might result in to the neuro-muscular act of raising my left arm, while the requirement that they add up to 2 might result in to the act of raising my right arm.)
Thus we can mount a good defense of human freedom by hypothesizing that human choices (which are holistic acts that are properly ascribed to persons) are capable of influencing lower-level events in the human body, such as activities taking place in nerve cells when they process incoming signals. Additionally, we may hypothesize that the operation of nerve cells is not always deterministic, or even deterministic most of the time with occasional random disturbances, but that fundamental, higher-level actions occurring in the brain (i.e. human choices) can constrain the microscopic behavior of nerve cells, and that these constraints, when aggregated over a large number of nerve cells, can result in neuro-muscular movements.
It seems to me, then, that in order to restore human freedom, we have to affirm at least two things: we have to say that people can influence their brains, and we have to say that top-down (macro->micro) causation is real and fundamental. For if causation is always bottom-up (micro->macro) and never top-down, or alternatively, if top-down causation is real, but only happens because it has already been determined by some preceding occurrence of bottom-up causation, then our actions are simply the product of our body chemistry – in which case they are not free, as they are determined by external circumstances which lie beyond our control. But if top-down causation is real and fundamental, then events occurring at a holistic level – including a person’s choices – can determine events at a microscopic level, such as their neuro-muscular movements.
The position we have now reached, then, is that if we want to defend human freedom, we have to believe that human acts (i.e. actions which are properly ascribed to persons and not to their body parts) can and do influence lower-level actions, which occur at various locations in the human body, such as activities taking place in human cells when they process incoming signals. We also have to say that the operation of cells is not always deterministic, or even generally deterministic with occasional random disturbances, but that fundamental, higher-level actions can shape the behavior of cells.
What might these higher-level actions be? It might seem tempting to say that higher-level bodily actions can bring about lower-level bodily actions. That’s fine, so far as it goes. However, if we are to have genuine freedom, then these higher-level bodily actions must be just as ontologically fundamental as the lower-level bodily actions that they determine. For if these higher-level actions are determined by lower-level bodily actions occurring at a previous time, then we are back at square one again: we are once more the prisoners of our body chemistry, and bottom-up causation rules.
Freedom and Immateriality: Two simple arguments based on the nature of thinking
Could a bodily action, even a higher-level one, be free? I would argue that it cannot, for several reasons. I’ll mention just two; Professor Feser has provided many more (see here, here, here, here and here).
First, free choices presuppose a capacity for abstract thinking. For instance, I can think about the number e, or the idea of justice, or the nature of an electromagnetic field. However, a process taking place at a particular point (or set of points) in my body is (by definition) not abstract but concrete. It follows that a bodily action is by its very nature incapable of instantiating an abstract concept.
Second, our mental acts – especially our free choices and the thoughts that accompany them – typically possess an inherent meaning, which lies beyond themselves. (In philosophical jargon, this kind of meaning is referred to as intrinsic intentionality.) However, brain processes cannot possess this kind of meaning, because physical states of affairs have no inherent meaning as such. (Neuronal firings don’t mean anything, in their own right.) Hence our thoughts and choices cannot be identified with our brain processes. As Professor Edward Feser put it in a recent blog post (September 2008):
Now the puzzle intentionality poses for materialism can be summarized this way: Brain processes, like ink marks, sound waves, the motion of water molecules, electrical current, and any other physical phenomenon you can think of, seem clearly devoid of any inherent meaning. By themselves they are simply meaningless patterns of electrochemical activity. Yet our thoughts do have inherent meaning – that’s how they are able to impart it to otherwise meaningless ink marks, sound waves, etc. In that case, though, it seems that our thoughts cannot possibly be identified with any physical processes in the brain. In short: Thoughts and the like possess inherent meaning or intentionality; brain processes, like ink marks, sound waves, and the like, are utterly devoid of any inherent meaning or intentionality; so thoughts and the like cannot possibly be identified with brain processes.
The foregoing is but a brief sketch of the argument that our thoughts are immaterial actions, which cannot be identified with any physical process, because they have properties that no physical process can possess. I discuss the argument in much further depth here. The point I would like to emphasize here is that I am not arguing that mind and body are two things; rather, what I am arguing is that a human being is a single entity, but that not every act of a human being is a bodily act.
The position we have now reached is that if we are to defend human freedom, we have to make a third affirmation; we have to affirm that some human actions (thoughts and choices) are non-bodily actions, and that by performing these actions, human beings are capable of influencing events occurring in the cells of their bodies. And since motor movements begin in the brain, we seem to be committed to the proposition that human beings can, by thinking and choosing, influence events in their brains.
The oddity of being human
This may sound odd. After all, not everyone knows that they even have a brain: many children don’t, and I imagine many people in times past didn’t know, either. How, it might be asked, can I possibly influence my brain simply by deciding to raise my arm, if I am not thinking about my brain as such, or if I don’t even know I have a brain?
My answer is that we just have to take it as a basic fact of human nature that whenever I perform the non-bodily action of deciding to move my right arm, region “X” of the motor homunculus in my brain (i.e. the area in my brain which governs right arm movements) is activated, and whenever I decide to move my right leg instead, region “Y” of the motor homunculus in my brain (which governs right leg movements) is activated.
“How convenient!” you might say. And it is. Indeed, it’s more than convenient – it’s absolutely extraordinary. If we were not made that way, voluntary action would be impossible. Since the soul is the form of the body only, I cannot will other objects to move; telekinesis is impossible. I can only move my body parts.
So my solution to the interaction problem is simply to say that God has made human beings with certain built-in psycho-physical correspondences between their (immaterial) mental acts of choosing to move different body parts, and the resulting movements of the various regions of the brain which govern these different body parts.
This might still sound a little mysterious, but let’s face it: there are many things in science which are a lot more mysterious. It is a mystery that there are laws of Nature, which accurately describe the behavior of bodies. It is also a mystery that these laws continue to hold, day after day. It is an even greater mystery that the laws of Nature manifest a mathematical elegance which awes even the world’s greatest physicists – an underlying beauty and symmetry which points to their being the product of a Mind. (The anthropic cosmological principle cannot explain this beauty: life-friendly laws of Nature need not be mathematically elegant.)
Let us remember, too, that a mystery is a different thing from an impossibility. Descartes’ dualism made it impossible for the soul to move the body; but the modified hylemorphic dualism I am proposing here merely makes it a peculiar “brute fact” about human beings that we have the strange ability to move our bodies by performing immaterial mental acts. This is a very odd thing, but if we recall that the soul is the form of the body, then it is no longer as odd as it might seem at first blush.
I am of course well aware that my account of the mechanics of voluntary movement is grossly oversimplified, as it overlooks such things as feedback, forward modeling, fine motor-tuning and proprioception. Many of these features are found even in insects, which are responsive to stimuli and capable of associative learning, but lack sentience. Now if people can voluntarily fine-tune their actions, then of course they need to be aware at a conscious level of what’s happening to their bodies when they move. However, I don’t think that we need to postulate any extra psycho-physical correspondences on that account. At the very most, we might need further correspondences between people’s mental acts of choosing and other parts of their nervous system, besides the motor homunculus in the brain.
I would like to conclude by saying that the problem of the relation between mind and body is a difficult one, no matter what your philosophical perspective. A modified version of hylemorphic dualism remains philosophically tenable and compatible with the scientific facts. Descartes’ dualism is a straw man. As for materialism, it’s an option that I would describe as “not even wrong” (to quote Wolfgang Pauli out of context), as it fails to address the simple question of how our thoughts come to possess meaning in their own right – which they cannot do if they are simply neural processes. If our thoughts lacked this kind of meaning, then human beings could never progress by exchanging ideas with one another. I am heartened by the fact that Professor Carroll, like myself, is a passionate believer in the power of human reason to discover truth, both in science and in philosophy.