Maverick Philosopher: Strictly Philosophical

A Hylomorphic Solution to the Interaction Problem?

Interactionist substance dualism in the philosophy of mind is supposed to face a devastating objection, the interaction objection. In the first part of this post I will present this objection in its traditional form and suggest that it is not all that serious. In the second part, however, I take the objection seriously and consider whether Aristotelian- Thomistic hylomorphism has the resources to counter it. 

I. The Traditional Interaction Objection

 It is a given that mind affects body, and body mind. Suddenly remembering the bottle of single-malt Scotch that Harry gave me for my birthday, I am inspired to get out of my chair and pour myself some. After consuming a generous portion, I note that my mental state has altered appreciably. The mental event of remembering causes the physical event of drinking which in turn elicits the mental state of elation, which may bring in its train some loss of motor control.  But how are such interactions possible if mind and body/brain are distinct types of substance, one spatial the other nonspatial? As Elliot Sober put it recently: 

If the mind is immaterial, then it does not take up space. But if it lacks spatial location, how can it be causally connected to the body? When two events are causally connected, we normally expect there to be a physical signal that passes from one to the other. How can a physical signal emerge from or lead to the mind if the mind is no place at all? (Philosophy of Biology ,Westview 2000, 2nd ed., p. 24) 

The above is a piece of philosophical boilerplate endlessly repeated in the materialist literature.  I confess to a difficulty in seeing just what this objection is supposed to be. If Sober is saying that all causation must involve physical contact between cause and effect, then he simply begs the question against the dualist. He simply asserts something that the dualist denies. Is it obvious what the correct theory of causation is?  Is it obvious that all causation involves physical contact between cause and effect and the transfer of some physical magnitude from cause to effect?  Certainly not inasmuch as there are a number of competing theories of causation, among them counterfactual theories, transfer theories, and nomological theories, to name just three broad types.  Given that the nature of causation is up for grabs, and given that the interaction objections requires a transfer theory of causation, one should conclude that the interaction objections is the exact opposite of decisive.

If interactionist dualism is true, then there are cases of causation that do not operate by physical contact. One cannot refute this by saying, or implying, that all cases of causation operate by physical contact. At this point I will be told that dualist interaction is unintelligible. But why? If you say that it is because dualist interaction does not fit the physical-physical pattern, then again you beg the question. If you say that every case of causation involves an intervening mechanism, but there isn't one in the dualist case, then you beg the question in a slightly more subtle way. For what the dualist holds is that there are cases of direct causation. It is not clear that all physical-physical causation is indirect, but even if it were, this putative fact is not a reason to think that all cases of causation are indirect.

But how does mental-physical causation work? If this is a demand for a specification of the intervening mechanism, then the question rests on a false presupposition, namely, that there must be such a mechanism. If, on the other hand, the demand is for a specification of the causally relevant properties and covering laws, then I see no reason why this demand cannot be met.

I think that there is less to the traditional objection than meets the eye: it gives the interactionist dualist little reason to abandon his view.   

II. A Hylomorphic Solution

But perhaps I'm wrong — in the good company of Curt Ducasse, John Foster and a few others. Legions of philosophers have taken the objection sketched above to be crushingly strong. A drastic way of meeting it is by retaining a dualism of substances while denying interaction. Occasionalists, parallelists, and epiphenomenalists deny interaction. But I mention them only to set them aside. An alternative is to hold to interaction while denying dualism. Here we meet materialists and idealists. But brevity is the soul of blog, so I set them aside as well. This brings us to what might be called hylomorphic dualist interactionism. Is it superior to substance dualist interactionism? That is the question.

For the hylomorphist, every material substance is a compound of form and matter. Human beings are no exception. In them, anima forma corporis: the soul is the (substantial) form of the body. Soul is to body as form to matter. The form and matter of a material substance are not themselves (primary) substances: they are not capable of independent existence. They are rather 'principles' uncovered in the analysis of material substances. This is a key difference between substance dualism and hylomorphic dualism. If the mind is a (primary) substance, then it can exist on its own, where 'can' expresses broadly logical possibility. But if the mind or soul is the substantial form of the body, then it cannot exist on its own. It needs matter both to exist and to be individuated.

Thus the hylomorphic dualist, while remaining a dualist, makes a significant concession to materialism. Human minds are essentially embodied minds. Before my conception, there was no res cogitans 'with my name on it,' so to speak. I did not pre-exist my conception. I came into existence at conception. (That I am wholly dissolved in death is not admitted by Thomists, inasmuch as they hold that the human soul is a subsistent form; but let us not worry about this special problem now.) Human minds are essentially enmattered minds in at least this sense: no human mind can exist without at some time being embodied. According to Edward Feser, a consequence of the hylomorphic view is that: 

. . . there is no mystery about how soul and body get into causal contact with one another, for the soul-body relationship is just one instance of a more general relationship existing everywhere in the natural world, namely, the relation between forms . . . and the matter they organize. If this general relationship is not particularly mysterious, neither is the specific case of the relationship between soul and body. The mistake of Cartesian dualists and materialists alike, according to the hylomorphist, is to think of all causation as efficient causation. When it is allowed that there are other irreducible modes of explanation — in particular, explanation in terms of formal causation — the interaction problem disappears. (Philosophy of Mind: A Short Introduction, p. 176) 

Feser here makes two main points. The first is the the soul-body relation is a special case of the form-matter relation; as such, the former is no more problematic than the latter. The second point is that the relation between soul and body is one of formal, not efficient, causation. The two points are logically connected: if the soul is the form of the body, and if the two are causally related, then it is difficult to see how the relation could be one of efficient causation. An efficient cause is either an agent-cause or an event-cause. But forms are neither agents nor events.

Hylomorphism undoubtedly reduces the 'ontological distance' between mind and body, a 'distance' that is troubling on substance-dualist conceptions, but I honestly do not see how hylomorphism solves the problem of interaction. We are assuming that there is interaction, two-way causal influence. We are also assuming dualism in a sense stronger than mere property-dualism: 'hylomorphism' is not just a name for a version of supervenience physicalism. Now interaction is, by definition, efficient-causal interaction. Mental events bring about physical events and physical events bring about mental events. To interpret this interaction in terms of formal causation seems tantamount to denying that there is any interaction. Iteraction is efficient-causal interaction. Formal causation appears irrelevant to it.

To revert to my example, my sudden remembering of having been given a bottle of Scotch is an event-token that enters into the etiology of my rising from my chair. It is rather unclear how this event could be the form of anything in the body. For one thing, the event of remembering is temporally prior to any of the events involved in my rising from my chair. Forms, however, are not temporally prior or posterior to what they inform. So it seems clear that a mental event cannot stand to a physical event it causes in the relation of form to matter.

Turning now to the contemporary Thomist John Peterson for instruction, we read: 

. . . it is just because Peter's human essence or form is in matter that Peter's intellect and will are not to be confused with the intellect and will of a pure spirit. But if this confusion is not made, then the question of how Peter's supposedly purely spiritual volitions can cause the movements of his arms and legs does not even arise. ("Persons and the Problem of Interaction," The Modern Schoolman, January 1985, p. 136) 

I fail to see how this does anything to solve the problem of interaction under the two conditions specified above, namely, that there is interaction, and that mind is irreducible to body. We are told that Peter's human essence is in matter. Fine, he is not a disembodied spirit. But that which thinks in me, if a res cogitans, is also not a disembodied spirit. So merely pointing out that a mind is not disembodied does nothing to solve the interaction problem. And saying that the mind is the form of the body also does nothing to solve the problem. For as I said above, the problem of interaction is a problem of efficient causation, not one of formal causation as alone would be be appropriate if the mind were the form of the body.

Whatever merits hylomorphism may have, it seem quite irrelevant to the interaction problem.

Interactionist substance dualism in the philosophy of mind is supposed to face a devastating objection, the interaction objection. In the first part of this post I will present this objection in its traditional form and suggest that it is not all that serious. In the second part, however, I take the objection seriously and consider whether Aristotelian- Thomistic hylomorphism has the resources to counter it. 

I. The Traditional Interaction Objection

 It is a given that mind affects body, and body mind. Suddenly remembering the bottle of single-malt Scotch that Harry gave me for my birthday, I am inspired to get out of my chair and pour myself some. After consuming a generous portion, I note that my mental state has altered appreciably. The mental event of remembering causes the physical event of drinking which in turn elicits the mental state of elation, which may bring in its train some loss of motor control.  But how are such interactions possible if mind and body/brain are distinct types of substance, one spatial the other nonspatial? As Elliot Sober put it recently: 

If the mind is immaterial, then it does not take up space. But if it lacks spatial location, how can it be causally connected to the body? When two events are causally connected, we normally expect there to be a physical signal that passes from one to the other. How can a physical signal emerge from or lead to the mind if the mind is no place at all? (Philosophy of Biology ,Westview 2000, 2nd ed., p. 24) 

The above is a piece of philosophical boilerplate endlessly repeated in the materialist literature.  I confess to a difficulty in seeing just what this objection is supposed to be. If Sober is saying that all causation must involve physical contact between cause and effect, then he simply begs the question against the dualist. He simply asserts something that the dualist denies. Is it obvious what the correct theory of causation is?  Is it obvious that all causation involves physical contact between cause and effect and the transfer of some physical magnitude from cause to effect?  Certainly not inasmuch as there are a number of competing theories of causation, among them counterfactual theories, transfer theories, and nomological theories, to name just three broad types.  Given that the nature of causation is up for grabs, and given that the interaction objections requires a transfer theory of causation, one should conclude that the interaction objections is the exact opposite of decisive.

If interactionist dualism is true, then there are cases of causation that do not operate by physical contact. One cannot refute this by saying, or implying, that all cases of causation operate by physical contact. At this point I will be told that dualist interaction is unintelligible. But why? If you say that it is because dualist interaction does not fit the physical-physical pattern, then again you beg the question. If you say that every case of causation involves an intervening mechanism, but there isn't one in the dualist case, then you beg the question in a slightly more subtle way. For what the dualist holds is that there are cases of direct causation. It is not clear that all physical-physical causation is indirect, but even if it were, this putative fact is not a reason to think that all cases of causation are indirect.

But how does mental-physical causation work? If this is a demand for a specification of the intervening mechanism, then the question rests on a false presupposition, namely, that there must be such a mechanism. If, on the other hand, the demand is for a specification of the causally relevant properties and covering laws, then I see no reason why this demand cannot be met.

I think that there is less to the traditional objection than meets the eye: it gives the interactionist dualist little reason to abandon his view.   

II. A Hylomorphic Solution

But perhaps I'm wrong — in the good company of Curt Ducasse, John Foster and a few others. Legions of philosophers have taken the objection sketched above to be crushingly strong. A drastic way of meeting it is by retaining a dualism of substances while denying interaction. Occasionalists, parallelists, and epiphenomenalists deny interaction. But I mention them only to set them aside. An alternative is to hold to interaction while denying dualism. Here we meet materialists and idealists. But brevity is the soul of blog, so I set them aside as well. This brings us to what might be called hylomorphic dualist interactionism. Is it superior to substance dualist interactionism? That is the question.

For the hylomorphist, every material substance is a compound of form and matter. Human beings are no exception. In them, anima forma corporis: the soul is the (substantial) form of the body. Soul is to body as form to matter. The form and matter of a material substance are not themselves (primary) substances: they are not capable of independent existence. They are rather 'principles' uncovered in the analysis of material substances. This is a key difference between substance dualism and hylomorphic dualism. If the mind is a (primary) substance, then it can exist on its own, where 'can' expresses broadly logical possibility. But if the mind or soul is the substantial form of the body, then it cannot exist on its own. It needs matter both to exist and to be individuated.

Thus the hylomorphic dualist, while remaining a dualist, makes a significant concession to materialism. Human minds are essentially embodied minds. Before my conception, there was no res cogitans 'with my name on it,' so to speak. I did not pre-exist my conception. I came into existence at conception. (That I am wholly dissolved in death is not admitted by Thomists, inasmuch as they hold that the human soul is a subsistent form; but let us not worry about this special problem now.) Human minds are essentially enmattered minds in at least this sense: no human mind can exist without at some time being embodied. According to Edward Feser, a consequence of the hylomorphic view is that: 

. . . there is no mystery about how soul and body get into causal contact with one another, for the soul-body relationship is just one instance of a more general relationship existing everywhere in the natural world, namely, the relation between forms . . . and the matter they organize. If this general relationship is not particularly mysterious, neither is the specific case of the relationship between soul and body. The mistake of Cartesian dualists and materialists alike, according to the hylomorphist, is to think of all causation as efficient causation. When it is allowed that there are other irreducible modes of explanation — in particular, explanation in terms of formal causation — the interaction problem disappears. (Philosophy of Mind: A Short Introduction, p. 176) 

Feser here makes two main points. The first is the the soul-body relation is a special case of the form-matter relation; as such, the former is no more problematic than the latter. The second point is that the relation between soul and body is one of formal, not efficient, causation. The two points are logically connected: if the soul is the form of the body, and if the two are causally related, then it is difficult to see how the relation could be one of efficient causation. An efficient cause is either an agent-cause or an event-cause. But forms are neither agents nor events.

Hylomorphism undoubtedly reduces the 'ontological distance' between mind and body, a 'distance' that is troubling on substance-dualist conceptions, but I honestly do not see how hylomorphism solves the problem of interaction. We are assuming that there is interaction, two-way causal influence. We are also assuming dualism in a sense stronger than mere property-dualism: 'hylomorphism' is not just a name for a version of supervenience physicalism. Now interaction is, by definition, efficient-causal interaction. Mental events bring about physical events and physical events bring about mental events. To interpret this interaction in terms of formal causation seems tantamount to denying that there is any interaction. Iteraction is efficient-causal interaction. Formal causation appears irrelevant to it.

To revert to my example, my sudden remembering of having been given a bottle of Scotch is an event-token that enters into the etiology of my rising from my chair. It is rather unclear how this event could be the form of anything in the body. For one thing, the event of remembering is temporally prior to any of the events involved in my rising from my chair. Forms, however, are not temporally prior or posterior to what they inform. So it seems clear that a mental event cannot stand to a physical event it causes in the relation of form to matter.

Turning now to the contemporary Thomist John Peterson for instruction, we read: 

. . . it is just because Peter's human essence or form is in matter that Peter's intellect and will are not to be confused with the intellect and will of a pure spirit. But if this confusion is not made, then the question of how Peter's supposedly purely spiritual volitions can cause the movements of his arms and legs does not even arise. ("Persons and the Problem of Interaction," The Modern Schoolman, January 1985, p. 136) 

I fail to see how this does anything to solve the problem of interaction under the two conditions specified above, namely, that there is interaction, and that mind is irreducible to body. We are told that Peter's human essence is in matter. Fine, he is not a disembodied spirit. But that which thinks in me, if a res cogitans, is also not a disembodied spirit. So merely pointing out that a mind is not disembodied does nothing to solve the interaction problem. And saying that the mind is the form of the body also does nothing to solve the problem. For as I said above, the problem of interaction is a problem of efficient causation, not one of formal causation as alone would be be appropriate if the mind were the form of the body.

Whatever merits hylomorphism may have, it seem quite irrelevant to the interaction problem.

Memory, Memory Traces, and Causation

Passing a lady in the supermarket I catch a whiff of patchouli.  Her scent puts me in mind of hippy-trippy Pamela from the summer of '69.  An olfactory stimulus in the present causes a memory, also in the present, of an event long past, a tête-à-tête with a certain girl.  How ordinary, but how strange! Suddenly I am 'brought back' to the fabulous and far-off summer of '69.  What is memory and how does it work?  How is it even possible? 

Let's start with the 'datanic' as I like to say:

1. There are (veridical) memories through which we gain epistemic access to the actual past, to events that really happened.  The above example is a case of episodic personal memory.  I remember an event in my personal past.  To be precise, I remember my having experienced an event in my personal past.  My having been born by Caesarean section is also an episode from my personal past, and I remember that that was my mode of exiting my mother's body; but I don't remember experiencing that transition.  So not every autobiographical memory is a personal episodic memory.  The latter is the only sort of memory I will be discussing in this post.  The sentence in boldface is the nonnegotiable starting point of our investigation. 

We now add a couple of more theoretical and less datanic propositions, ones which are not obvious, but are  plausible and accepted by many theorists:

2. Memory is a causal notion.  A mental image of a past event needn't be a memory of a past event.  So what makes a mental image of a past event a memory image?  Its causal history.  My present memory has a causal history that begins with the event in 1969 as I experienced it.

3. There is no action at a temporal distance.  There is no direct causation over a temporal gap.  There are no remote causes; every cause is a proximate cause.  A necessary ingredient of causation is spatiotemporal contiguity.  So while memory is a causal notion, my present memory of the '69 event is not directly caused by that event.  For how could an event that no longer exists directly cause, over a decades-long temporal gap, a memory event in the present?  That would seem to be something 'spooky,' a kind of magic. 

Each of these propositions lays strong claim to our acceptance.  But how can they all be true?  (1) and (2) taken together appear to entail the negation of (3).  How then can we accommodate them all?

Memory trace theories provide a means of accommodation.  Suppose there are memory traces or engrams engraved in some medium.  For materialists this medium will have to be the brain.  One way to think of a memory trace is as a brain modification that was caused at the time of the original experience, and that persists since that time.  So the encounter with Pam in '69 induced a change in my brain, left a trace there, a trace which has persisted since then.  When I passed the patchouli lady in the supermarket, the olfactory stimulus 'activated' the dormant memory trace.   This activation of the memory trace either is or causes the memory experience whose intentional object is the past event.  With the help of memory traces we get causation wthout action at a temporal distance. 

(Far out, man!)

The theory or theory-schema just outlined seems to allow us to uphold each of the above propositions. In particular, it seems to allow us to explain how a present memory of a past event can be caused by the past event without the past event having to jump the decades-long temporal gap between event remembered and memory.  The memory trace laid down in '69 by the original experience exists in the present and is activated in the present by the sensory stimulus.  Thus the temporal contiguity requirement is satisfied.  And if the medium in which the memory traces are stored is the brain or central nervous system, then the spatial contiguity requirement is also satisfied.

Question:  Could memory traces play merely causal roles?

Given (2) and (3), it seems that memory traces must be introduced as causal mediators between past and present.  But could they be just that?  Or must they also play a representational role?  Intuitively, it seems that nothing could be a memory trace unless it somehow represented the event of which it is a trace. If E isthe original experience, and T is E's trace, then it it seems we must say that T is of E in a two-fold sense corresponding to the difference between the subjective and objective genitive.  First, T is of E in that T is E's trace, the one that E caused. Second, T is of E in that T represents E. 

It seems obvious that a trace must represent.  In my example,the sensory stimulus (the whiff of patchouli) is not of or about the '69 event.  It merely activates the trace, rendering the dispositional occurrent.  But the memory is about the '69 event.  So the aboutness must reside in the trace.  The trace must represent the event that caused it  -- and no other past event.  The memory represents because the trace represents.  If the trace didn't represent anything, how could the memory -- which is merely the activation of the trace or an immediate causal consequence of the activation of the trace -- represent anything?  How a persisting brain modification -- however it is conceived, whether it is static or dynamic, whether localized or nonlocalized -- can represent anything is an important and vexing question but one I will discuss in a later post.

Right now I want to nail down the claim that memory traces cannot play a merely causal role, but must also bear the burden of representation.

Suppose a number of strangers visit me briefly.  I want to remember them,  but my power of memory is very weak and I know I will not remember them without the aid of some mnemonic device.  So I have my visitors leave calling cards.  They do so, except that they are all the same, and all blank (white).  These blank cards are their traces, one per visitor.   The visitors leave, but the cards remain behind as traces of their visit.  I store the cards in a drawer.  I 'activate' a card by pulling it out of storage and looking at it.  I am then reminded (at most) that I had a visitor, but not put in mind of any particular visitor such as Tom.  So even if the card in my hand was produced by Tom, that card is useless for the purpose of remembering Tom.  Likewise for every other card.  Each was produced by someone in particular and only by that person; but none of them 'bring back' any particular person. 

Bear in my mind that I don't directly remember any of my visitors.  My only memory access to them is via their traces, their calling cards.  For the visitors are long gone just like the '69 experience.  So the problem is not merely that I don't know which card is from which person; the problem is that I cannot even distinguish the persons.  

Had each visitor left a differently  colored card, that would not have helped.  Nor are matters helped if each visitor leaves a different sort of trace; a bottle cap, a spark plug, a lock of hair, a guitar pick.  Even if  Tom is a guitar player and leaves a guitar pick, that is unhelpful too  since I have no access to Tom except via his trace. 

So it doesn't matter whether my ten visitors leave ten tokens of the same type, or ten tokens each of a different type.  Either way I won't be able to remember them via the traces they leave behind.  Clearly, what I need from each visitor is an item that uniquely represents him or her -- as opposed to an item that is merely caused to be in my house by the visitor.  Suppose Tom left a unique guitar pick, the only one of its kind in existence.  That wouldn't help either since no inspection of that unique pick could reveal that it was of Tom rather than of Eric or Eric's cat.  Ditto if Tom has signed his card or his pick 'Tom Riff.'  That might be a phony name, or the name of him and his guitar -- doesn't B. B . King call his guitar 'Lucille'?

If I can remember that it was Tom who left the guitar pick, then of course I don't need the guitar pick to remember Tom by.  I simply remember Tom directly without the need for a trace.  On the other hand, if I do need a trace in order to remember long gone Tom, then that trace must have representational power: it cannot be merely something that plays a causal role. 

Traces theories have to avoid both circularity and vicious infinite regress.

Circularity.  To explain the phenomenon of memory, the trace theory posits the existence of memory traces.  But if the explanation in terms of traces ends up presupposing memory, then the theory is circular and worthless.  If what makes the guitar pick a trace of Tom is that I remember that Tom left it, then the explanation is circular.  Now consider the trace T in my brain which, when activated by stimulus S causes a memory M of past experience E.  M represents E because T represents E.  What makes T represent E? What makes the memory trace caused by the encounter with Pam in '69 represent Pam or my talking with her?  The answer cannot be that I remember the memory trace being caused by the encounter with Pam.  For that would be blatantly circular.  Besides, memory traces in the brain are not accessible to introspection.

Infinite Regress.  Our question is: what makes T represent E and nothing else?  To avoid circularity one might say this:  There is a trace T* which records the fact of E's production of T, and T represents E in virtue of T*.  But this leads to a  vicious infinite regress.   Suppose Sally leaves a photo of herself.  How do I know that the photo is of Sally and not of her sister Ally?  If you say that I directly remember Sally and thereby know that the photo is unambiguously of her, then you move in a circle.  You may as well just say that we remember directly and not via traces.  So, to hold onto the trace theory, one might say the following:  There is a photo of Sally and a photo of her photograph, side by side.  Inspection of  this photo reveals that the first photo is of Sally.  But this leads to regress:  what makes the second photo a photo of the first?

Conclusion:  To avoid both circularity and infinite regress, memory traces must possess intrinsic representational power.  Their role cannot be merely causal.

A later post will then address the question whether memory traces could have intrinsic representational power.  If you are a regular reader of this blog you will be able to guess my answer, namely, that nothing of a merely material nature has intrinsic representational power.

REFERENCE:  John Heil, "Traces of Things Past," Philosophy of Science, vol. 45, no. 1 (March 1978), pp. 60-72.  My calling card example above is a reworking of Heil's tennis ball example.

Existence and Power: Commentary on Plato's Sophist 247e

At Sophist 247e, Plato puts the following into the mouth of the Eleatic Stranger:

I suggest that anything has real being that is so constituted as to possess any sort of power either to affect anything else or to be affected, in however small a degree, by the most insignificant agent, though it be only once.  I am proposing  as a mark to distinguish real things that they are nothing but power. (Cornford tr.)

The gist of the passage is that what makes a thing real or existent is its (active) power to affect other things or its (passive) power to be affected by them.  In sum,

D. For any x, x exists =_df x is causally active or passive.

Thus everything causally active/passive exists, and only the causally active/passive exists.  The definition rules out of existence all 'causally inert' items such as propositions as Frege construes them, namely, as the senses of context-free indicative sentences. And of course it rules out sets of Fregean propositions.  But what about the mathematical (as opposed to commonsense) set of the books on my desks?  Each of the books is existent or real by (D) and so is the object resulting from the bundling of the books together; but the set of these books is arguably abstract and thus causally inert.  So if (D) is true,  we cannot admit mathematical sets into our ontology.  For such items do not enter into causal relations.  Fregean propositions and mathematical sets are therefore putative counterexamples to (D).  If these counterexamples are genuine then (D) fails extensionally: the extension of the existent is wider than the extension of the causally active/passive.

But what interests me at the moment is not the extensional correctness of (D) but  a deeper question.  Even if we assume that (D) is extensionally correct, i.e., that all and only  existents are causally active/passive, does (D) tell us what it is for an item to exist?  When we say of a thing that it exists, what are we saying about it?  That it is causally active/passive?  My answer is in the negative -- even if we assume that all and only existents are causally active/passive.

My reason is quite simple.  For an item to be capable of acting or being acted upon it must 'be there' or exist!  'Before' it can be a doer or a done-to it must exist. (The 'before' is to be taken logically not temporally.) The nonexistent cannot act or be acted upon.  There is no danger that winged horses will collide with airplanes.  The reason is not that winged horses are abstract or causally inert objects; the reason is that they do not exist.  Winged horses, if there were any, would belong to the category of the causally active/passive.  But they don't exist -- which is the reason why they cannot act or be acted upon.  They are not abstract items but nonexistent concrete items.  Existence, therefore, is a necessary condition of an item's being a causal agent or patient.  It follows that existence cannot be explicated in terms of power as per the Eleatic Stranger's suggestion.  Existence is too fundamental to be explicated in terms of power -- or anything else.

If you are having trouble seeing the point consider the winged horse Pegasus and his singleton {Pegasus}.  Both of these items are nonexistent.  One is concrete (causally active/passive) while the other is abstract.  But neither can enter into causal relations.  To say that Pegasus is concrete is to say that Pegasus, were he to exist, would belong among the causally active/passive.  What prevents him from being such is his nonexistence.  His existence, therefore, cannot be explicated in terms of causal activity/passivity.

There is a tendency to conflate two different questions about existence.  One question about existence concerns what exists.  Answers to this question can be supplied in the form of definitions like (D) above.  But there is a  deeper question about existence, namely, the question as  what it is for an existing thing to exist.  What I have just argued is that this second question cannot be answered with any definition like (D).  For even if you find a definition that is extensionally correct and immune to counterexamples, you will at the very most have specified the necessary and sufficient conditions for a thing's  being among existing things.   You will have not thereby have put your finger on what it is for an existing item to exist. 

Suppose you say that, 

For any x, x exists  =_df x has properties. 

This proposal has an excellent chance of being extensionally correct: necessarily, everything that exists has properties, and everything that has properties exists.  But the proposal does not get at the existence of an existing thing precisely because it presupposes the existence of existing things.  This is because all such definitions are really circular inasmuch as they have the form:

For any x, x exists =_df x is ____ and x exists.

Existence itself eludes definitional grasp.  Even if the existent can be defined, the Existence of the existent cannot be defined.  For more on this fascinating topic, see my A Paradigm Theory of Existence (Kluwer 2002), pp. 2-8.