Gottfried Wilhelm Von Leibniz	Rene Descartes

Leibniz & Descartes on Matters of the Mind

Introduction to Leibniz
The soul/mind is a dominant monad. But what is a monad? Here are some of the monad's properties:

1. his capacity to understand the perceptions of the one monad, and the monad's perceptions, the entire past, present and future. [See: Theodicy sect.360; Discourse on Metaphysics sect.8; Monadology sect.22] Because every monad is numerically simple (i.e., indivisible, unlike material things, which are infinitely divisible in virtue of being made up of parts), only two of its characteristics can make it so that one is distinguishable from the other (by God, and to some extent, by us, via reason): (i) its internal qualitative complexity, and
   
   
2. its appetition, which is the "tendencies from one perception to the other".
     But all monads have appetition. So how can appetition help individuate monads? The answer lies in the fact that perception of all things is of varying degrees. To simplify matters, consider the following example. You are on a hilltop overlooking a beautiful city at night, holding a mirror; the reflective side of the mirror is facing the city lights. One area on the mirror clearly reflects the tallest building, say, the Sony building. On the bottom right corner there is a faint reflection of the tiny Hitachi building. And so on. Some buildings are reflected more clearly than others, and some reflections are so faint that you can barely make out what they are reflections of (like the car parked on the corner). More or less in this way, the monad reflects every aspect of the universe in varying degrees of clarity, though of course the reflections will not be simple picture-like images. change All changes from one perception to the other in the monad takes place internally, via an internal principle of change. As previously stated, the monad isn't really affected by external things. It just seems that way because it is 'pre-programmed' to perceive or mirror the things around it. This is what Leibniz calls "pre-established harmony".

God creates monads at t1 (though time isn't real for Leibniz, this temporal factor will serve as elucidatory here), and at t1, it has already been astablished that in 2565, for instance, this particular monad will reflect the statue of liberty to degree of clarity .8, and the car on the corner to degree .001, etc.

Does Leibniz believe in the Immortality of the soul?
The misleadingly simple answer is, "of course the soul is immortal for Leibniz!" in a sense, they are. But this doesn't mean that souls jump from one person (or dog) to another. To understand what stays behind, what doesn't, and in what sense, we need to first grasp Leibniz's notion of a dominant monad, which will do much of the work.

Leibniz was a brilliant man; so when he's kind enough to help us out by providing analogies, we should take seriously his expectation that the analogy should advance our understanding. So let's consider this: he compares the dominant monad to an entertainer which around which a herd of people gather to see a performance. The herd here represents the regular monads, and the performer represents the dominant monad.
  There is an important sense in which the dominant monad guides the body, and other, (more submissive, so to speak) monads. This is so even though there is no real, typical causation-like guidance here. Each monad and, derivatively, the compound material body, is pre-programmed to do everything it does. I will touch on this issue of guidance later on. Now more on these dominant monads.

Interaction of body & mind; pre-established harmony
The dominant monad has clearer, more distinct perceptions, than the rest of the monads that make up (what we would view as) a whole person. This is what corresponds most closely to what we call "mind".
  On Descartes' view, the extended material body really receives material input from the surrounding world; this information is relayed, via the animal spirits, to the mind (or soul). Thus material things, for Descartes, have the ability to move the body (causing it to move, via true, clasically mechanical, impact), and they even have the capacity to cause changes in what the mind perceives (indirectly) via the sense organs, in what it imagines (when it rearranges ideas to form new ones), and in what we store in our memory. No such impact is possible on Leibniz's view.
  As we have seen, harmony is pre-established between mind and body for Leibniz. So in a manner of speaking, it 'just so happens' (though it's no accident) that you see a red apple when the red apple is before your eyes. But more surprisingly perhaps, it just so happens that your hand moves when you will it to move. Both the movement and the willing were already pre-programmed to happen: it was necessary that those things were going to happen, given that God programmed us that way.
  How does God program us? By programming the monads somehow--by impregnating them with the future. So the monads have a built-in mechanism of change (which indicates the sense in which they are "automata" or "machines"). This mechanism of change is called "appetition". But this, according to Leibniz, does not detract from our freedom.
  Moreover, Leibniz claims to have avoided the problems that bedeviled Descartes' mind-body interaction. Leibniz states that Descartes gave up on this problem (and Leibniz was probably right, although not all Descartes' writings have survived--perhaps he addressed the problem in the lost works). Descartes didn't account for how it is that the mind, a self-subsistent non-extended, indivisible and spiritual substance could possibly come into contact with body so as to interact with it so intimately, as he claimed it did. The body is necessarily an extended material (also self-subsistent) substance, for Descartes.
  How could two things, essentially opposites in nature, interact at all--like Descartes says they do? We could claim, perhaps, that it is futile to ask what the interaction might be like exactly because one of the entities involved is the mind. That is, perhaps the interaction must be incomprehensible. This wouldn't entail that there could be no such interaction. But it doesn't look like Descartes is allowed to give this answer. For according to him, we are aware of all the operations of the mind! There is no unconscious thought. If this is true, how could we be unaware of the interaction between mind and body? I'm not convinced that Descartes' notion of conscious thought includes the awareness of interaction. It certainly includes awareness that there is interaction, but I'm not convinced that it is supposed to include awareness of all the operations of the mind. But this is not a topic I can address here.
  But the problem is more serious than this for Descartes. For the interaction of material substances has always been cashed out in terms of impact--classical impact-motion--for Descartes. He goes on at lengths (and in venerable detail) about the mechanisms of material body. And it is safe to say that explaining the internal workings and sub-mechanisms of any body was extremely important to Descartes. So it seems, at least from his existing works, that he actually might have evaded the entire problem, or that he just didn't care much! That's my own opinion, to be defended elsewhere. The fact that he often promises to deal with the problem, and doesn't, might either be indicative of the fact that he deliberately avoided it, or never got around to it, or perhaps that an explanation was to be found in his other, lost works.
  It is often suggested that Descartes' animal spirits play a role, however small, in solving the interaction problem. But this is silly. The animal spirits, Descartes urges ad nauseum, are material things. The question would remain: how do they interact with the soul? You can't solve the interaction problem by substituting body for a part of the body--namely, the animal spirits.

Leibniz doesn't seem to have this problem. For he denies outright that there is any such interaction. It is no surprise that there seems to be interaction, for both body and mind are pre-programmed to be in perfect harmony with one another. They are also so programmed in the best possible way--so as to play a part in forming the best possible world (in conjunction with the assumption of his principle of the best, this could not but have been the world that God chose to create in the beginning). Leibniz doesn't see this as problematic with respect to freedom. But his argument that this has to be the way things are goes like this:

The mind and body can be 'conjoined in three possible ways
  (i) the way of influence (Descartes' interaction)
  (ii) the way of assistance (occasionalism)
  (iii) the way of pre-established harmony (Leibniz's system)

(i) is immediately ruled out; Leibniz claims it is not wise to think that somehow, the particles of material substances can enter into the immaterial substance, or vice versa. This is, in essence, the problem with Descartes' interactionism.

(ii) won't do either; God created the world at the beginning, and put things into motion then and there, programming things in such a way that they would not require further assistance in order to do what it is they will do. Because God foresees everything, there is no need for him to 'do things twice', so to speak: he gets it right the first time around (and what theist of his time would argue with that without getting punished for it?!).

So (iii) is the right view.

Loose Definitions

animal spirits (Descartes)
Miniscule particle-like material things in bodily fluid that are capable of travelling through the body at an astonighinsly fast speed; they are directly responsible for relaying information to the soul, which is 'seated' and has its primary effects in the pineal gland in the brain (just behind the eyes).

pineal gland (Descartes)
An area of the brain where the soul is said to have its primary effects with respect to guiding the body and receiving information from the sense organs. Descartes mistakenly believed that only human beings have a pineal gland (other animals also have one). He posited this as the area where the soul is 'seated' (metaphorically speaking) because, unlike other parts of the brain and body, of the pineal gland there is only one (Descartes was very well-(self-)taught in anatomy). The fact that there is only one heart lead him to initially wonder whether it was the seat of the soul. But he concluded that the pineal gland was the better candidate. The fact that he knew that other animals also have hearts probably played a role in his opting for the pineal gland.