Martin Knutzen: System of efficient causes, or a philosophical commentary on explaining the interaction of mind and body by physical influx (1745)

If there was one mainstay in pre-Kantian German philosophy, it was the question of the interaction between soul or mind and body. Thus, it is no wonder that we find Martin Knutzen, best known as the teacher of Kant, also tackling the question in his Systema causarum efficientium seu commentatio philosophica de commercio mentis et corporis per influxum physicum explicando.

The setting of the question is clear. We find that certain states of our mind correspond to certain states of our body. This is evident in case of sensations, when e.g. a visual experience corresponds to our eyes receiving light rays. Similar correspondence happens in some cases with emotions, for instance, when a feeling of rage is connected to rapid movement of heart. Finally, often our volitions (like me wanting something to eat) correspond to bodily movements (me moving toward the kitchen). Such correspondence asks for an explanation, Knutzen says, and it is the duty of philosophers to come up with such explanations.

As is familiar, three possible explanations were provided for the correspondence: firstly, the theory of physical influx, according to which mind and body really act upon each other, occasionalism, according to which God in each individual case arranges mind and body to change their state accordingly, and pre-established harmony, according to which mind changes its state according to its own laws and body according to its own laws, but God has ordered these changes to harmonise, when designing the world.

Knutzen does not add any further type of explanation, but suggests that these three explanations were the only ones possible. Explanation, he suggests, requires finding the cause for the correspondence. Such a cause can be either intrinsic to a human being as a combination of mind and body or extrinsic to it. If it is extrinsic, then we are suggesting, in the vain of occasionalism, that some entity outside the human being makes e.g. an arm move, whenever a certain type of volition occurs in the human mind. If the cause is intrinsic to a human being, Knutzen continues, then either one part of the human being (mind or body) affects the other part – this is obviously what the theory of physical influx says – or mind and body form closed causal chains, states of mind affecting further states of mind and states of body affecting only further states of body. In the latter case, the correspondence or harmony of mind and body is just a brute fact, which must then be further explained, as in the theory of pre-established harmony, by God fixing the causal chains of mind and body to harmonise with one another.

How then to decide between the three systems? Knutzen notes that the question cannot be decided by experience, since we cannot literally perceive mind and body acting on one another or God intervening in the causal chains, not to mention God making before the creation of mind and body a decision to harmonise them. What we are then left with is to find some reasons why we should prefer one system over the others.

Knutzen’s strategy is to ground his reasoning in the philosophical paradigm in Germany of his time, that is, Wolffian philosophy, by making references to Wolff’s works, whenever possible. Thus, Knutzen begins by pointing out that mind or soul is a simple substance, which has both intellect and free will and particularly has representations of its own body. As a simple substance, he continues, the mind is immaterial, while the body is a composite of many parts. Then again, even bodies must ultimately be composed of simple substances or elements, since otherwise a body would have an infinite amount of parts, which Knutzen thinks an absurd idea.

Knutzen goes on by defining what an action means: a thing acts, when it has in itself a reason why something else exists or changes. The reason in question is called a force, which is thus a tendency to act or generate and change things. Furthermore, Knutzen adds, force is always a sufficient reason for acting, that is, if no obstacle prevents, force generates an action, no matter what.

Following Leibniz’s relational definition, Knutzen takes space to be an order of coexisting things. A place of a thing is then just a definite mode of being in that order or of relating to other things. Thus, at least finite substances cannot exist in the same place at the same time. Motion, furthermore, is a change of place: thing changes its relation to other things. Because this change affects only the relations of a thing, it does not intrinsically affect the moving thing. The motion is still based on something more substantial, Knutzen says, namely, the motive force making a thing move.

All existing things must be determined in every manner, Knutzen says. Particularly, their relations to other coexisting things must also be determined, in other words, they must exist in some definite place. This truth, Knutzen continues, holds also of simple substances, such as the elements of the bodies. Furthermore, since bodies move, elements must also move. Then again, they do not fill a space or have an extension, since they have no parts, of which they would consist.

Two things cannot occupy the same place at the same time, which means, Knutzen suggests, that a thing resists the other taking its place. When a thing moves, it takes the place of another thing, in other words, it must overcome this resistance through some force. Particularly, Knutzen concludes, the elements of the body must use force to overcome this resistance of other elements and push them away, thus, the elements truly affect one another. Since a cause can be known from its effect (an accepted truth in Wolff’s ontology), we could even say that through changes caused by other elements an element represents or perceives other elements.

If elements act upon another, we can thus say that some simple and perceiving things interact with each other. This raises the probability of the mind also interacting with its body, Knutzen suggests, since the mind would interact with the body by interacting with the elements, of which the bodies consist. Of course, there is still a possibility that a mind would be different from elements on this point: perhaps interaction with elements of matter is somehow an imperfection that would not befit the status of a mind. Yet, Knutzen points out, God is thought to act on elements, and as God is absolutely perfect, the interaction with elements cannot be an imperfection.

In addition to showing the probability of the system of physical influx or real interaction of the mind and the body, Knutzen adds some further points to convince the reader the choose this system over the others: occasionalism is based on God doing constant miracles, while the system of pre-established harmony cannot explain why the bodies should be created in the first place. Furthermore, Knutzen also tries to directly prove the truth of the interaction. Just like other simple substances, a human mind must exist in some place, and indeed, it exists in a place where it is constantly together with its body. Thus, the mind must move with its body. Either it is passively moved by the body – and the interaction is real – or mind moves itself – and then it must be able to push other simple things around it, in other words, to interact with them.

Opponents of the physical influx had often stated that such an influx is just an empty word that has no meaning. Knutzen thinks this is a false accusation, since we have a perfectly good explanation of what physical influence means: real interaction of a mind and its body. Then again, he admits we cannot completely comprehend what the physical influx is like, since an interaction of simple things is something we cannot fully understand: we humans require distinctions in our cognition, but such an interaction can only happen instantaneously and no distinctions can be made in instantaneous changes. This is still no detriment to the truth of physical influx, since there are many things, Knutzen says, we can know to be true, although we cannot intuitively grasp them.

A further common objection to the system of physical influx was that it breaks the law of nature which states that the quantity of the motion in the universe cannot be changed: when I will my hand to move, I create new motion. Knutzen’s answer is that this supposed law is based only on observations of material objects and their interactions and that we need not suppose that it is correct for the interaction of the mind and the body.

Knutzen also considers the objection that we really cannot derive a force for moving material objects from a force of representing things, which should be the essence of a human mind. Knutzen thinks such a derivation is fairly simple. A force of representation, he explains, does not mean just a passive capacity to represent things, but active striving to try to represent things. Since representations of the mind correspond to the states of the body, the force of representation must also involve a force to change the body and its place in the universe.

Finally, Knutzen answers some objections that suggest physical influx would degrade the worth of a human mind. Firstly, he says, physical influx does not make the mind completely passive and dependent on the body, since the mind can also affect the body and does also have activities beyond interaction with the body.

Furthermore, Meier continues, physical influx does not contradict the immortality of the mind. Such a denial of immortality was based on the supposition that since the theory assumes sensations to be caused by the body, the destruction of the body would lead to a life with no sensations and thus without any consciousness. Knutzen notes that there is no reason why we shouldn’t get new bodies after our death. In addition, even if we did not get a new body, we might have sensations of other kinds, such as direct experience of other minds. Finally, Knutzen concludes, even if we wouldn’t have any sensations, our mind could still do a lot of things, such a abstract reasoning, which would entail consciousness.

Christian August Crusius: Instruction to live reasonably (1744)

(1715-1775)

Although most important of Christian Wolff’s critics, Adolph Friedrich Hoffmann, did not have the chance to publish anything beyond logic of his system, we could view the work of his student, Crucius, as a sort of completion, and furthermore, as a conduit, through which basic anti-Wolffian ideas were transmitted to Kant.

The first book of Crucius I shall be looking at, Anweisung vernünftig zu leben, is almost at the opposite of spectrum from the methodological work of Hoffmann, that is, the interest of Crucius lies in the question how to live well. But before studying that question, Crucius says, we must first investigate the nature of human will. While in Wolffian school this study was a part of psychology - itself a part of metaphysics - Crucius noted that human will could not actually be a topic of metaphysics, which should study only what is necessary. Instead, Crucius introduced a completely new discipline, thelematology, dedicated just to human will.

A further difference from Wolffian practices is the definition of will Crucius endorses. While Wolffians usually distinguished will as a rational faculty from sensible appetite, Crucius saw will more as having irrational and rational modifications - in other words, instead of the difference between animals and human beings, Crucius emphasised the difference between mere material and animated objects.

In addition, the relation between representation and will was somewhat different with Wolffians and with Crucius. While Wolffians apparently defined appetite and will as a capacity for certain type of representations - irrational or rational representations of good and evil - and actions flowed in a seemingly necessary manner from these representations, for Crucius will was more a power to act according to representations. In other words, Crucius thought that representations provided a mere model for action, while will was the cause actualising these models. Indeed, Crucius said that without will a representing entity couldn’t act. Still, Crucius noted, there isn’t really any merely representing entities, because representations of such an entity would be completely purposeless, and God never creates anything without a purpose.

Capacity for representations - what Crucius calls understanding - is then, he says, dependent on will as its goal. Then again, will is also dependent on understanding, Crucius continues, because without representations provided by understanding will wouldn’t have anything to act in accordance with. Despite this mutual presupposition, Crucius insisted, the two capacities must be based on different basic forces - that is, when we are speaking of finite entities, while with God understanding and will are merely different names for one infinite force. In case of finite entities, on the other hand, representing something does not explain why the entity strives for something, and similarly, striving for something does not explain why the entity has representations.

Will acts for some purposes, Crucius says, although in a sense we speak of purposes only when the subject of willing knows distinctly what it strives for. In a sense, this notion of purpose, Crucius notes, can mean three distinct, but related things. Firstly, we may say that the subject strives for some state of itself or subjective purpose, for instance, when Alexander the Great wanted to receive the title of the high king of Persia. Secondly, the subject may be said to strive for some external object or objective purpose, for instance, when Alexander the Great was interested of the realm of Persia. Finally, the subject strives for a formal purpose, that is, to be in some relation to the objective purpose, for instance, when Alexander the Great wanted to subject Persia under his rule.

Will, Crucius notes, is free, when and in so far as it could be directed to another purpose than it happens to be directed. When this freedom of will is applied, a person is said to make a decision. On the contrary, when will continues to strive for some purpose without any decision, Crucius defines will to be controlled by a drive. Some of the drives are basic or belong to the essence of the person, while other drives are essential or contingent consequences of these basic drives.

Once a striving of human will is fulfilled, Crucius says, the person enters into a state of pleasure, while a contrary state of events leads person into a state of pain. Because human being is controlled by many drives, a person can experience many types of pleasure and pain. Crucius notes that we have no reason to assume that other animals are conscious of anything, thus, we have no reason to assume they feel pleasure or pain. On the other hand, Crucius thinks that God can feel pleasure, but no pain, because God’s will is always fulfilled.

Crucius defines good and evil in terms of will: what is good for a person is what is in accordance with her will, while evil for a person is what is contrary to her will. This is only a relative notion, Crucius says, and against Wolffians, he is quick to distinguish good from perfection. Crucius does note that there is an absolute or metaphysical sense of goodness, as what is in accordance with God’s will.

Although will and understanding are two different forces, Crucius noted, will can affect understanding, because human beings can think purposefully. Will does not have a complete control over understanding, Crucius says, because it also follows its own laws, for instance, association, but it can at least determine how long understanding considers something. Furthermore, Crucius insisted that will could be said to affect itself in the sense that certain desires and drives could have an effect on one another and the power of decision could also affect the desires and drives.

In addition to understanding and itself, Crucius was certain that will - or more accurately, the whole soul of human being - could affect body, because when we earnestly willed to move healthy limbs, the limbs truly moved. Crucius explicitly argued against occasionalism by saying that God could not continuously act as a mediator between soul and body, because it would be below the status of divinity. Probably against the Leibnizian notion of pre-established harmony Crucius noted that God would not have created world, if it had no interaction with souls (what Crucius appears to have missed is the Berkelyan possibility that material world might not exist at all). Crucius admitted that this interaction could not be explained, because we did not know the nature of souls nor of the smallest parts of bodies. Still he was certain that we could know why God had to provide the possibility of the interaction - finite spirits had to exist in some definite place and not omnipresently, like God, thus, they had to be able to change their position in relation to other things.

A move toward accepting the soul-body -interaction had happened also within the Wolffian tradition. A more notably anti-Wolffian stance in Crucius’s thelematology was his insistence that will was free in a strong sense of not being externally coerced nor internally necessary. Crucius defended his position, firstly, through a need to take ethics seriously: unless will would be free in a strong sense, we would have no reason to praise or condemn the actions of a person and becoming virtuous would be down to mere luck.

A more metaphysical reason for believing the possibility of free will, Crucius noted, is that a series of causes must finally come back to an uncaused cause or basic activity. True, he admitted, not all basic activities were free: elemental activities are by nature continuously actualised, while other basic activities, like that of human understanding, are bound to certain conditions, but by their nature inevitable, whenever these conditions are in place. Free will differs from these other basic activities, because its actions are only made possible by external conditions, but free will is still required to turn this possibility into an actuality. To make matters more complicated, Crucius noted that finite understanding cannot demonstrate beforehand whether free will would actualise some possibility, but infinite understanding or God could know it intuitively.

While his ethical and metaphysical arguments for free will were not completely foolproof, Crucius had to rely on a mere assurance that we are conscious of being able to do things otherwise. He admitted that some philosophers had held this idea to be mere imagination. Yet, he concluded, God must have created some freely acting entities, so that creation as a whole would have some purpose.

Free will, Crucius assured, was not against the principle of sufficient reason, because all generated things do need a cause. Where Wolffians had went wrong was in insisting that the cause would always be completely determined to produce only a certain result - something that Wolff himself might actually have agreed upon. Furthermore, Crucius was also aware that we are not always completely free - we do have drives that might restrict our decisions, and we might require considerable effort for diminishing the hold of drives. Only God has a completely free will, which is not restricted by anything - true, God can will only things in conformity with his goodness, but, Crucius argued, this was merely an explanation of what kind of things God wills.

This is what we would usually hear about Crucius’s notion of will in a treatise on history of philosophy. But I would like to go all the way through this book and see how Crucius applies these abstract notions to more concrete questions. Next, I’ll be looking at the general properties of human desires.

Joachim Darjes: Elements of metaphysics 2 – Mind-body-interaction

No German metaphysician at the middle of 18th century could avoid the question what happens between soul or spirit and body, and Darjes is no exception to this trend. He is quite clear that soul and body are in some measure harmonious, that is, from occurrings in body it is possible to know something about occurrings in soul and vice versa. He is also quite explicit that this harmony is not complete, in other words, that there are actions in body or soul that are not reflected in the actions of the other.

Wolffian school recognised three different solutions to the mind-body problem: firstly, the assumption that soul and body had some real causal influence to one another, secondly, the occasionalism, according to which God bridged the divide between soul and body, and thirdly, the Leibnizian pre-established harmony. Like everyone else in Wolffian school, Darjes does not take occasionalism seriously, because it contradicts the freedom of human actions. Furthermore, like many philosophers of his generation, Darjes does not necessarily respect the traditional Wolffian answer or the pre-established harmony. Indeed, Darjes notes that because harmony of soul and body is to be explained, just assuming the existence of such a harmony is no real answer.

The only respectable option in Darjes' eyes is then the assumption of real interaction between soul and body. Like his wont always, Darjes makes intricate distinctions. He notes that body influences soul in quite a different manner than soul influences body. As a spontaneously active entity, soul cannot be affected by a causal chain originating outside it. Instead, Darjes argues, some movement in the nervous fluid can only remove impediments from the activities of soul and thus give occasion to some sensuous representation. Soul, on the other hand, should have the ability to casually influence nervous fluid and through it whole body.

Darjes concludes his account of rational psychology with few remarks on activities of soul and ways to classify souls and spirits and put them into a hierarchy (it is no wonder that he places soul requiring perceptual content in a lower rung than pure spirit). What we might still point out is his remark that soul cannot be said to be present in a single place in the body, but in the whole body and all its organic parts.

Joachim Darjes: Elements of metaphysics 2 – Souls and bodies

The final chapters in Darjesian empirical psychology concern the interaction of soul with the body. He is not yet trying to explain this interaction – explanations belong more to the next section or rational psychology. Thus, Darjes is now merely out to note the various situations where such interaction occurs.

Darjes begins by saying that we observe a certain complex entity or body as one constituent in my existence. Indeed, he notes, this body is a mechanistic machine or a system of non-spontaneous entities, and just like all machines, it can only work through motions. Now, at some situations we perceive that certain motions within my body – e.g. those occurring in my sense organs – correspond with certain cognitive states. When these movements stop, this specific cognitive state stops, when the movements change, so does the cognitive state, and finally, if some internal state of the body, like a disturbance in blood circulation, confuses the movements, the cognitive state becomes also confused and doesn't become clarified until the confused state of the body stops.

Clearly what Darjes has been describing is sensation, which is one type of the so-called inferior cognitive faculty. Yet, Darjes notes, not all inferior cognitive faculty need not have so close connection to motions of body. This is especially true of imagination, which associatively moves from one representation to another, which it has often been connected with. Thus, while the original representation might have a connection with actual motions in my body, the second representation might have no such connection. Furthermore, the association makes it also possible that superior cognition has some connection with motions of our body. In other words, we can use sensuous symbols to represent e.g. universal conceptions and so make it possible that motions of body awaken certain universal thoughts in us.

In addition to the relation of body with human cognition, Darjes also considers the relation of appetites and aversions with body. He firstly notes that appetites and aversions by themselves do not produce any motions in our bodies – if we just crave for food, this still does not make us do anything. One must also have made a decision on the means by which e.g. our hunger should be dealt with, and this decision of means will then be followed by movement of our body. Although body by itself is a system of non-spontaneous entities, because of this relation to spontaneous choices of human soul we can call certain motions of our bodies spontaneous and free. On the other hand, certain motions in our body have no such relation to spontaneous choices and can then be called forced motions.

Reasonable thoughts on the use of parts in humans, animals and plants (1725) and Singular phenomenon of fruit-bearing apple recalled all the way from blossoming to physical reasons (1727)

Wolff's physical writings continue: a book on general physical processes and another book on the purposes of physical processes are followed by a book concentrating specifically on biological questions, Vernünfftige Gedancken von dem Gebrauche der Theile in Menschen, Thieren und Pflanzen.

As we have seen earlier, biology and especially botanic was a topic Wolff himself had empirically investigated. It is then no wonder that the book feels quite professional and up-to-date, even if Wolff cannot yet know e.g. how leaves actually nourish plant in their interaction with carbon dioxide: it is enough that he can describe leaves and their parts and understands that they have something to with the nourishment of plants. Wolff goes carefully through all parts of human body, beginning from different types of fibers – the smallest elements of living matter known at that time – and all organs made out of these elements, and if necessary, he compares parts of human body with parts of other animals. After humans and animals, similar treatment waits plants.

What is somewhat striking is Wolff's open attitude towards even the most taboo questions of human bodies, particularly sexuality. Description of sexual organs was frowned upon, because reading about genitalia was thought to incite people to perversities. Wolff, on the other hand, thinks that information about sexuality will help a person to fulfill sexual needs in a moral manner: you cannot do something properly, if you don't know the reasons for it. Interestingly, Wolff is aware of the role of clitoris in female sexuality and thinks it has been created for awakening in women the want of intercourse - a necessary precondition of having children. Wolff also suggests that sexual pleasure is especially meant to encourage women to want sexual intercourse: otherwise they might refrain from it, because they feared the burden of child birth.

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As it should be evident, Wolff is not satisfied with mere description of living beings, but is also concerned to find the reason why God created them in the first place. The answer is actually familiar already from Wolff's teleology: humans and other rational entities exist in order to witness the glory of creation, and other things, including living entities, are meant to serve rational beings and their needs.

Wolff adds to this general description of the purpose of animals and plants two interesting details. Firstly, while Wolff's official teleological account of the world is an example of what later was called external teleology (things have a purpose beyond themselves), he also notes that animal and plant species could also be regarded as having an internal purpose that does not require reference to things beyond that species. Wolff suggests that this internal purpose would be propagation of species: animals and plants exist to produce other plants and animals of the same type. Thus, from the viewpoint of a certain plant, it is contingent that we use its flowers for medicinal purposes, but on the other hand, it is relevant that the flower produces seeds.

Secondly, Wolff also adds an aesthetic layer to his teleology. That is, he suggests that God does not just create purposive animals and plants, but that God's creations are also beautiful or pleasing to senses. Wolff especially emphasizes the symmetricity of animals as an evidence of their beauty: it just looks better if I have two ears equidistant from the center of the face and not, for instance, one on left hand and other on stomach.

Philosophically most interesting part of Wolff's biology are the little details that shed some more light on the question of the interaction of soul and body. Wolff refrains from the central question, whether and how soul and body interact, on the pretext that this is more of a metaphysical than biological problem. Yet, he points out that the problem concerns actually the interaction between the soul and the brain, which then controls the rest of the body. The exact details of this control are still not known to Wolff. Wolff is aware of nerves, but he doesn't really know how they work, so he must rely on Cartesian idea that there are some mysterious animal spirits that help nerves turn volitional movements of brain into movements of muscles, although instead of spirits, Wolff prefers the more material concept of nerve juice.

Before ending this post, I shall just quickly note that Wolff was actually more involved with biological studies at this time, because in a few years he published an inaugural dissertation celebrating his new post at the university of Marburg, Phaenomenon singulare de malo pomifera absque floribus ad rationes physicas revocatum, which is based on the botanical research of Wolff and his follower Thümmig.

So much for Wolff's biology. In next post, I shall investigate a Wolffian we have already met a number of times, tackling now metaphysics.