The mind-body connection is absolutely present when we suffer loss and grief and can induce significant changes in the body, such as increasing stress-induced hormones.
One way of avoiding this scandal is to say that mental and physicalevents occur in parallel, without calling for interaction or a doctrine of mind-bodycausality. This approach was adopted by Malebranche (1638-1715), who invoked God to keepthe mental and the physical events in step. Secular versions of or the doctrine of concomitance have been widespread in the nineteenth andtwentieth centuries. For example, they were held by the philosopher, psychologist andevolutionary thinker, Herbert Spencer, by John Hughlings Jackson, the father of modernneurology, who adopted it from Spencer, and by Freud, who applied Jackson's ideas in hisfirst book, (1891) and continued to hold this view until his lastwriting, (1940).
This conclusion in the Sixth Meditation asserts the well-knownsubstance dualism of Descartes. That dualism leads to problems. AsPrincess Elisabeth, among others, asked: if mind isunextended and matter is extended, how do they interact? This problemvexed not only Descartes, who admitted to Elisabeth that he didn't have a good answer (3:694), but it also vexed Descartes' followers and othermetaphysicians. It seems that, somehow, states of the mind and the body must be brought into relation, because when we decide to pick up a pencilour arm actually moves, and when light hits our eyes we experience thevisible world. But how do mind and body interact? Some of Descartes'followers adopted an occasionalist position, according to which Godmediates the causal relations between mind and body; mind does notaffect body, and body does not affect mind, but God gives the mindappropriate sensations at the right moment, and he makes the body moveby putting it into the correct brain states at a moment thatcorresponds to the volition to pick up the pencil. Other philosophersadopted yet other solutions, including the monism of Spinoza and thepre-established harmony of Leibniz.
In mechanizing the concept of living thing, Descartes did not denythe distinction between living and nonliving, but he did redraw the linebetween ensouled and unensouled beings. In his view, among earthlybeings only humans have souls. He thus equated soul with mind: soulsaccount for intellection and volition, including conscious sensoryexperiences, conscious experience of images, and consciouslyexperienced memories. Descartes regarded nonhuman animals as machines,devoid of mind and consciousness, and hence lacking in sentience. (Although Descartes' followers understood him to have deniedall feeling to animals, some recent scholars question thisinterpretation; on this controversy, see Cottingham 1998 and Hatfield2008.) Consequently, Descartes was required toexplain all of the powers that Aristotelians had ascribed to thevegetative and sensitive soul by means of purely material andmechanistic processes (11:202). These mechanistic explanationsextended, then, not merely to nutrition, growth, and reproduction, but also to the functions of the external and internal senses,including the ability of nonhuman animals to respond via their senseorgans in a situationally appropriate manner: to approach things thatare beneficial to their body (including food) and to avoid danger (asthe sheep avoids the wolf).
In the Meditations, Descartes changed the structure of theargument. In the Second Meditation, he established that he could notdoubt the existence of himself as a thinking thing, but that he coulddoubt the existence of matter. However, he explicitly refused to usethis situation to conclude that his mind was distinct from body, on thegrounds that he was still ignorant of his nature (7:27). Then, in theSixth Meditation, having established, to his satisfaction, the mark oftruth, he used that mark to frame a positive argument to the effect thatthe essence of mind is thought and that a thinking thing isunextended; and that the essence of matter is extension and thatextended things cannot think (7:78). He based this argument on clearand distinct intellectual perceptions of the essences of mind andmatter, not on the fact that he could doubt the existence of one or theother.
As previously mentioned, Descartes considered theMeditations to contain the principles of his physics. Butthere is no Meditation labeled “principles of physics.” The principlesin question, which are spread through the work, concern the nature ofmatter (that its essence is extension), the activity of God in creatingand conserving the world, the nature of mind (that it is an unextended,thinking substance), mind–body union and interaction, and theontology of sensory qualities. (Descartes and his followers included topicsconcerning the nature of the mind and mind–body interaction within physics ornatural philosophy, on which, see Hatfield 2000.)
The problem is thus in no way solved if we can show that all the facts, they were known to a single mind (as we hypothetically assume them to be given to the observing economist), would uniquely determine the solution; instead we must show how a solution is produced by the interactions of people each of whom possesses only partial knowledge. To assume all the knowledge to be given to a single mind in the same manner in which we assume it to be given to us as the explaining economists is to assume the problem away and to disregard everything that is important and significant in the real world.
After publication of the Discourse in 1637, Descartesreceived in his correspondence queries and challenges to various of thedoctrines, including his account of the sequence of phenomena duringheart-beat and the circulation of the blood; his avoidance ofsubstantial forms and real qualities; his argument for a distinctionbetween mind and body; and his view that natural philosophicalhypotheses could be “proven” through the effects that they explain(6:76). Descartes' correspondence from the second half of the 1630s repays close study, among other things for his discussions of hypothesis-confirmation in science, his replies to objectionsconcerning his metaphysics, and his explanation that he had left themost radical skeptical arguments out of this work, since it was writtenin French for a wide audience (1:350, 561).
Taken literally, this statement is simply untrue. The consumers do nothing of the kind. What Professor Schumpeter's presumably means is that the valuation of the factors of production is implied in, or follows necessarily from, the valuation of consumers' goods. But this, too, is not correct. Implication is a logical relationship which can be meaningfully asserted only of propositions simultaneously present to one and the same mind. It is evident, however, that the values of the factors of production do not depend solely on the valuation of the consumers' goods but also on the conditions of supply of the various factors of production. Only to a mind to which all these facts were simultaneously known would the answer necessarily follow from the facts given to it. The practical problem, however, arises precisely because these facts are never so given to a single mind, and because, in consequence, it is necessary that in the solution of the problem knowledge should be used that is dispersed among many people.
After suppressing his World, Descartes decided to putforward, anonymously, a limited sample of his new philosophy, in theDiscourse with its attached essays. The Discourserecounted Descartes' own life journey, explaining how he had come tothe position of doubting his previous knowledge and seeking to beginafresh. It offered some initial results of his metaphysicalinvestigations, including mind–body dualism. It did not, however,engage in the deep skepticism of the later Meditations, nordid it claim to establish, metaphysically, that the essence of matteris extension. This last conclusion was presented merely as a hypothesiswhose fruitfulness could be tested and proven by way of its results, ascontained in the attached essays on Dioptrics andMeteorology. The latter subject area comprised“atmospheric” phenomena. In his Meteorology,Descartes described his general hypothesis about the nature of matter,before continuing on to provide accounts of vapors, salt, winds,clouds, snow, rain, hail, lightning, the rainbow, coronas, andparhelia.
The extant Principles offer metaphysics in Part I; the generalprinciples of physics, in the form of his matter theory and laws ofmotion, are presented in Part II, as following from the metaphysics;Part III concerns astronomical phenomena; and Part IV covers theformation of the earth and seeks to explain the properties of minerals,metals, magnets, fire, and the like, to which are appended discussionsof how the senses operate and a final discussion of methodologicalissues in natural philosophy. His intent had been also to explain in depth theorigins of plants and animals, human physiology, mind–body unionand interaction, and the function of the senses. In the end, he had toabandon the discussion of plants and animals (Princ. IV.188),but he included some discussion of mind–body union in his abbreviated account of the senses.