Two Models of The Soul

Here is a major choice point: is the soul part of the whole substance (the human person or organism) or not?

What does it mean for something to be part of some whole? Or, equivalently, what does it mean for something to be a whole composed of certain parts? I propose the following necessary condition on part/whole composition:

Whole-part supervenience principle (WPSP). The facts about a composite whole supervene on the facts about its proper parts.

Accepting WPSP does not mean rejecting Aristotelian holism, the view that wholes can be “more than the sum of their parts”. Holism means that certain properties (accidents) of a substance can be irreducible to the accidents of the substance’s proper parts. Let’s call these holistic accidents.

A holistic accident of the whole is still supervenient on the accidents of the proper parts, but it is ground-theoretically and explanatorily prior to at least some of those accidents. In some cases, the accidents of the parts are grounded or formally caused by the form and holistic accidents of the whole. Supervenience is simply a thesis about how properties correlate across possible worlds: it is completely neutral on which properties are prior and which are posterior. So, we can suppose (with the WPSP) that holistic accidents supervene on the properties of the proper parts while denying that the properties of the parts are explanatorily prior to the holistic accidents. That is, supervenience does not entail grounding.

Why accept WPSP? It strikes me as essential to the composition relation. If some fact about the whole does not supervene on the facts about a supposedly complete inventory of its proper parts, we must have missed at least one part. A whole can be in some respects prior to its parts, but it cannot be something over and above those parts.

If we accept the WPSP and we rule that the soul is not a part (in the relevant sense) of the substance, then we have no reason to suppose that the soul itself is the bearer of any accidents. All the relevant accidents could be borne by the whole substance and its material parts. On this picture, a soul or substantial does not undergo any intrinsic change or alteration. Any change to the soul must be merely a Cambridge change. The soul’s formal action (its causing the existence, extent, and essential nature of the whole organism and its parts) does vary over time, since the soul is constantly interacting with the whole organism, its parts, and their accidents. That is, the soul’s formal powers are conditional powers—powers to produce certain results under certain circumstances. The varying exercise of such conditional powers does not entail any intrinsic change in the soul itself.

On the alternative view, the soul is a part of the whole organism. This gives us the option of making the soul the bearer of certain accidents, which thereby expands the supervenience basis for the accidents of the whole. If the soul has accidents, then it can be changed intrinsically. It would have to have passive causal powers (potentialities). If we are going to attribute such passive powers to it, we might as well also confer on it active causal powers of the efficient sort, that is, powers to cause changes in other entities, including the organism and its material parts. This results in an interactionist model of the soul/body relation, that is analogous to that of Cartesian dualism. There’s still at least one significant difference between hylomorphic interactionism and dualist interactionism: for the hylomorphist, the soul is responsible (via its formal powers) for the existence, extent, and essential nature/organization of the body. The causal powers of the body and its parts still depend metaphysically on the soul.

It would be useful to have convenient names for the two hylomorphic models. Let’s call the first model emanationist and the second interactionist. Emanationism indicates that the influence of the soul on the body is a one-way street, and it avoids the suggestion that the soul acts upon the body in anything like an efficient way. Thomas Aquinas’s version of hylomorphism was clearly interactionist. He held that the soul had two aspects: as form of the body, and as motor (agent acting upon the body).

Emanationist model

1. The soul (form) is not part of the organism (substance).
2. The soul bears no accidents.
3. The soul has no causal powers that are per se efficient, i.e., powers that are essentially directed toward the causation of change.

Interactionist model

1. The soul is part of the organism.
2. The soul bears its own accidents.
3. The soul has causal powers that are per se efficient: powers essentially directed toward causing change in the body.

There are, in principle, six additional models, but these seem the two most internally coherent. If, for example, we deny that the soul can have accidents, then what is gained by counting it as part of the whole organism, as opposed to an external principle of it? And, if the soul is subject to being altered by external agents, why deny it the power to act reciprocally on external patients?

The Emanationist model is closer to Platonism than the Interactionist one in respect of its theory of form, since for Emanationists, the substantial form is impassible, intrinsically unchangeable. However, since Platonists do not identify souls with Forms, it is the Interactionist model that most resembles Plato’s dualism about the soul and the body.

However, the Emanationist model of form fits Aristotelian realism (with its real multiplication of forms by individuation) better than it fits Platonism. Even though the Emanationist soul does not interact with the body, its formal activity does cooperate with the accidents and parts of the body, and with the accidents and forms in the body’s immediate environment. There are distinct activities of cooperation corresponding to each substance in the infima species: what my soul does in maintaining the continuity and integrity of my body is unaffected by the vicissitudes affecting your body (except insofar as you are acting on me).

There’s an important distinction in Aristotle between movement (kinesis) and activity (energeia). Activity can also be translated as operation (operatione in Latin). Aristotle (in De Anima I) proposes that souls do not undergo motion but are subject to intrinsic change in a broader sense, changing from one mode of operation to another. An operation is the actualization of one of the soul’s (active) powers. It is the soul itself in a particular state of actuality, not a distinct entity (like an accident). Unlike alterations and other motions, an operation is not the effect of the action of an external agent. There may be required conditions (in the body) for an operation of the soul, but these conditions do not act on the soul.

So, how are accidents and operations different? First of all, each species of accident is a determinate of some determinable: like scarlet of color, or 1 kg of mass. Determinables have two important features: any two determinates of the determinable are mutually incompatible (contrary), and exemplifying a determinable necessitates the exemplifying of one of its determinates. The species of operations are not like this. Typically, any two operations are mutually incompatible, and all of the species of operation of a particular genus can be absent. It’s probably the case that no substance can exist without engaging in at least one operation, but these operations do not group themselves into determinables.

A second difference lies in the causation of accidents and determinables. A process of change (kinesis) in accidents (quantities, qualities, relative position) must be initiated by some external agent, exercising an appropriate causal power. The initiation of an operation, in contrast, is caused by the substance itself. The initiation may involve external conditions, but these conditions can be entirely passive, in the domain of potentiality rather than actuality.

Consequently, we can distinguish two versions of the Emanationist Model: the Pure Emanationist model (according to which the soul is absolutely unchangeable intrinsically, even in respect of its operations) and the Operationalist model.

It seems that the initiation of an operation of the human soul always requires an appropriate bodily condition (brain state). However, it is a separate question to ask: does the continuation of an operation requires any such bodily condition? If there are psychic operations that do not require any such bodily condition, then the survival of a human soul in a disembodied state is conceivable.