Kant’s Second Paralogism, On the Simplicity of the Soul

In the second paralogism, Kant continues to develop his critique of rationalist (Cartesian) psychology. He now turns his attention from its substantiality to its simplicity. A more or less common sense notion of simplicity at the outset will bring us a long way toward understanding its importance as a philosophical notion. In a nutshell: simplicity is a lack of complexity. A multicellular organism, for example, is more complex than a unicellular one; anything having fewer parts than another thing is more simple and less complex; and anything that is entirely one and without parts is absolutely simple.

Simplicity, like many other topics Kant addresses played an important role in the philosophical tradition. In medieval characterizations of God, for example, it was held that God is more simple than any created being. For Aquinas, this meant that He was, unlike more complex material things, one with his essence, giving Him an absolute simplicity. Being immaterial, God was held to be one with his form. With no material individuation and no possibility of change within the structure of His being, God’s immaterial immortality God’s being could be understood as pure Being. As such, there was said to be “no real distinction“ between his existence and his essence.

As will become progressively more clear, there are many parallels between the notion of divine simplicity and the simplicity of the soul that work their way into the discussion of the Cartesian/rationalist doctrine of the soul, which is the account of the soul Kant set out to critique. This surfaces most prominently where the notion of a substratum comes into play.

In what follows, Kant’s critique of the rationalistic doctrine of the soul’s simplicity will be discussed. The difficulty of the text calls for a close reading. Acordingly, a few of major concepts will be developed, with an eye to developing a smooth and hopefully, convincing, interpretation.

Stage Setting

In the Paralogisms, Kant undertakes a critique of the rationalist doctrine of the soul, a doctrine that putatively follows from first principles. In the second paralogism, we find him connecting the simplicity of the soul (in the rationalist account) to the prior notion of its substantiality in the following way:

… It is impossible that a thought should inhere in what is essentially composite. It is therefore possible only in a single substance, which, not being an aggregate of many, is absolutely simple.

(A352)

It will be the goal of what follows to understand these lines in a way that makes the rationalist doctrine seem possible before turning to Kant’s critique of it. This part of the Critique is not as straightforward as might have been hoped; nevertheless, taking it piece by piece, its elements may be more clearly discerned.

Let’s begin by considering the following claims that emerge from the quotation above:

1. If anything thinks it must be essentially one

hence,

2. The I that thinks, being a substance, must be a simple substance

The substantiality of the Cartesian soul was discussed and critiqued in our earlier discussion of the First Paralogism. Our primary concern at present will be to understand how the first claim is justified. What is it, in other words, about thinking that requires us to regard the soul as something simple as opposed to something complex? Alternatively, why can’t a thing that thinks be complex?

Complex vs. Simple Souls

Deciding what Kant means by the term “composite” (see the quotation from A352 above) is a necessary first step. The way in which these lines might apply to the soul in particular needs some clarification. Two possibilities may be considered. “Complex”might refer (a) to the intellect and the body taken together; or it may refer (b) to the I in the succession of its thoughts. While (a) might seem a more natural fit for the term “complex” in a discussion of the soul, (b) fits best with the ensuing discussion and with the second edition.

Simply put, the difference between a “simple” I and a “composite” one shows up more straightforwardly as the difference between a simple I that persists as one unified consciousness throughout the succession of its thoughts and a complex “I” that amounts to a succession of I-subjects that arise with each new thought-object.

On this reading, the “aggregate of many” substances mentioned in the quotation from A352 above can be understood as a succession of substantial I-subjects contrasted with the simple I that persists as one through the succession of its objects.

Internal vs. External Action

Next we must attend to Kant’s distinction between external and internal action. The description of external action on the basis of which internal action may be discussed, runs as follows:

An action rising from multiple contributing substances is only possible when its effect is external.”

A352

This might be briefly restated as the claim that

• If there is an action of any kind and it arises from a complex source (such as multiple contributing substances), then its effect must be external

“External” in this context may be understood as referring to an alteration or change that is effected upon something outside of or apart from the complex substance responsible for the change.

The example of a wheel (notice where Kant mentions “the motion of a body” in A355) may be instructive. When a wheel roles, each of its parts contributes to the action of the whole. The wheel rolls only when all of its parts act together as an aggregate. This type of action might be referred to as “aggregate action“ for short (not a term Kant uses). It may be noticed that the rolling action of the wheel is not directly effected by an internal change of its parts. A wheel does not roll by the replacement it’s spokes, for example. Instead, it relies upon a stability and uniformity of its parts, each contributing to the activity of the whole.

But things are quite different where the activity of thinking is concerned. The mind has the potential to think and, when it does, it is changed internally with respect to the changing content of its thoughts and its capacity for learning. Unlike the case of the wheel whose activity is external, the internal effect of thinking involves the growth of experience and understanding, which occurs by virtue of a continual alteration of the content of our thoughts as the thinking I passes from one object to another.

The very structure of a thought depends upon the presence of an object and without an object no thinking may take place. The internal effect created by thought, whether it be a judgment, the act of understanding, or of learning is not an effect that arises in something apart from the intellect, but an ongoing alteration occurring within itself.

Returning to the quote from A352 immediately above and its reconstruction, it is clear that if the effect of thought is considered to be internal, then it’s source (the causal agent) must be something non complex, hence, simple.

The I as One

Let’s take stock of the Kantian I emerging from his Critique. As was said, it is simple. The intellect itself is one and simple, yet it undergoes alterations internal to its activity when it thinks. An analogy that comes to mind is the relationship between the light of a film projector and a film strip. The light is not changed but the process of projection (thought) goes on as long as a film strip continues to run.

Each frame contributes to the development of one coherent image. The light corresponds to the I; the film strip to the objects that may be “loaded” into the form of a judgement. In this sense, it is also very “much like the substrate” of matter (A359): it is one and unchanging relative to the accidents it supports.

But Kant is most insistent that we are limited to a transcendental, general concept of the I as a thinking thing. That is to say, our representation of the I can never be anything other than a representation of something simple, “which never contains a synthesis of the manifold” (A356). Just as the proposition “I [who think] am substance” (A356) has no empirical correlate, so the proposition “I who think am simple” may only be regarded as noumenal in the negative sense: as something intelligible that lacks any empirical content. It is only in this sense that the I that acts as the absolute subject of our thoughts can be regarded either with regard to its substantiality or its simplicity: as a concept, but not as an object.

Mind/Body Dualism

With these concepts in hand, it might be wondered where this takes us as far as Cartesian mind/body dualism is concerned. The answer is that it leads to the dissolution of any basis for a distinction between the two.

Kant’s conclusions develop from his reduction of the I to a substrate that can be understood no further than as a “something.” Regarding the Cartesian notion of a substantial bodies, he notices, we would likewise not be able to proceed any further. As a substrate, the thinking I would be indistinguishable from the substratum of material substances.

This is due to the lack of sensible predicates (none in fact) that may be applied in either case. All that might be said of either one is that the ideas we have of them are consistent with the idea of simplicity (see A359-361). In fact, as Kant’s second edition makes clear, his final position regarding its substantiality delimits it in conceptual terms to its role as the logical subject of accidents.

Because of the lack of any sensible predicates that might serve to characterize the two independently of one another, all that might be said in either case is that any concept we might have of a substrate must be understood in purely noumenal terms. The result is a dissolution of any distinction that might serve to differentiate the two.