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Continuing with my publication on the science of psycology today I want to talk about the particular psycological theories about "The dual theory of René Descartes". We know that the different psychological theories try to describe different important aspects about our personality, our behavior, our development cognitive and our motivations, among many other issues. Below you can see some brushstrokes on one of the psychological theories that have been sculpting what we know about the human mind.

The dualistic theory of René Descartes establishes that the mind and the body are two entities of different nature, that the first has the power to control the second and that they interact with each other somewhere in the brain.

It is, basically, the transformation in theory of a kind of philosophical position of dualism, one of whose major representatives is Plato. Although the theory of Cartesian dualism has been formally discarded for decades, it continues to adopt new forms and remains implicit in the way in which many investigations in psychology and neuroscience are focused. In some way, it "infiltrates" the thinking of many research teams without their realizing it, which is why it is still relevant, even though it is not valid.

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René Descartes was a typical example of Renaissance intellectual: soldier, scientist, philosopher and speculative psychologist. He studied with the Jesuits, and his training was both metaphysical and humanistic. Its influence has been decisive for its reformulation of rationalism, and its inclusion in a mechanistic system.

Descartes (1596-1650) and Rationalism

Just as the skepticism of the Sophists was answered by Plato's rationalism, Descartes's rationalism was a response to the humanistic skepticism of the earlier period which, having placed man at the center of the world, did not trust his own forces to sustain it.

Descartes did not accept the skeptics' belief in the impossibility of knowledge, nor in the weakness of reason. He decided to systematically doubt everything until he found something that was so diaphanously true that it could not be doubted. Descartes discovered that he could doubt the existence of God, the validity of sensations (empiricist axiom), and even the existence of his body.

Cogito ergo sum: the first and undoubted truth

He continued in this way, until he discovered that he could not doubt one thing: of his own existence as a self-conscious and thinking being. There can be no doubt that there is doubt, because, in doing so, the action itself is denied. Descartes expressed his first undoubted truth with the famous: Cogito ergo sum. I think, therefore I am.

From his own existence, Descartes justified the existence of God through arguments that were put in doubt even then. He also established the existence of the world and of one's body, and the general accuracy of perception.

Descartes believed that a correct method of reasoning can discover and prove what is true. He advocates, as a good rationalist, the deductive method: to discover the obvious truths by reason and to deduce the rest from them. This method is opposed to the inductive method proposed by Francis Bacon and adopted by the empiricists.

Descartes, however, did not rule out the usefulness of the senses, although he thought that the facts have little value until they are ordered by reason.

From Philosophy to Psychology and knowledge about cognition

Descartes was not the first to justify his own existence in mental activity. Already the first rationalist, Parmenides, had affirmed "Because thinking and being is the same", and Saint Augustine had written "If I deceive myself, I exist" (for Descartes, however, who doubts all transcendent Truth, the question would have been " if I deceive myself, I do not exist "), and only a century before, according to Gomez Pereira:" I know I know something, and whoever knows exists. Then I exist. "The Cartesian novelty is to sustain the full meaning of doubt, and to cement the only certainty in logical truth.

From Descartes the philosophy will become more and more psychological, seeking to know the mind through introspection, until the appearance of psychology as an independent scientific discipline, in the nineteenth century, based on the study of consciousness through the introspective method (although only for the first generation of psychologists).

Descartes affirms the existence of two types of innate ideas: on the one hand the main ideas, those of which there is no doubt, although they are potential ideas that require experience to be updated. But it also speaks of innate ideas about certain ways of thinking (what we would now call processes, without specific content, only ways of operating: for example, transitivity). This second kind of innatism will be developed in the eighteenth century by Kant, with his a priori synthetic judgments.

Universal Mechanism

Descartes enriches Galileo's theory with principles and notions of mechanics, science that had achieved spectacular successes (watches, mechanical toys, fountains). But it is also Descartes the first to consider mechanistic principles as universal, applicable both to inert matter and to living matter, to microscopic particles as well as to celestial bodies.

The mechanistic conception of the body in Descartes is as follows: the characteristic of the body is that of being res extensa, material substance, as opposed to res cogitans or thinking substance.

These different substances interact through the pineal gland (the only part of the brain that does not repeat hemispherically), affecting each other mechanically.

The body has receptive organs and nerves or hollow tubes that internally communicate some parts with others. These tubes are traversed by a kind of filaments that at one end join with the receptors, and at the other with pores (as a cover) of the ventricles of the brain that when opened allow to pass through the nerves " animal spirits ", which influence the muscles causing movement. He did not distinguish, therefore, sensorial and motor nerves, but he had a rudimentary idea of ​​the electrical phenomenon that underlies nervous activity.

The legacy of René Descartes in other thinkers

It will be Galvani, in 1790, who, from the verification that the contact of two different metals produces contractions in the muscle of a frog, demonstrates that electricity is capable of causing in the human body similar effect to that of the mysterious "spirits" animals ", from which it could easily be inferred that the nervous impulse was bioelectrical in nature. Volta attributed this effect to electricity, and Galvani understood that it was generated by the contact of two metals; From the discussion between both arose, in 1800, the discovery of the battery, which initiated the science of electric current.

Helmholtz, in 1850 thanks to the invention of the miógrafo, measured the reaction delay of the muscle when stimulated from different lengths (26 meters per second). The mechanism of the sodium pump would not be discovered until 1940.

The importance of the pineal gland

the pineal gland, Descartes places the point of contact between the spirit (res cogitans, thinking substance) and the body, exercising a double function: control over excessive movements (passions) and, above all, consciousness. Since Descartes does not distinguish between consciousness and consciousness, he deduced that animals, which did not possess a soul, were like perfect machines without a psychological dimension, that is, without feelings or consciousness. Ya Gómez Pereira had denied the psychological quality of the sensation in the animals, leaving their movements reduced to complicated mechanical responses of the nerves acting from the brain.

The result was that a part of the soul, traditionally associated with movement, became an intelligible part of nature and, therefore, of science. Psychological behaviorism, which defines psychological behavior as movement, is indebted to Descartes' mechanicism. The psyche was configured, on the other hand, only as a thought, a position that would reappear later with cognitive psychology, if this is defined as the science of thought. For Descartes, however, thought was inseparable from consciousness.

A characteristic, however, common to these approaches, as widely happens in the rest of the modern sciences, is the radical separation between the subject that knows and the object of knowledge. Both movement and thought will become automatic, proceeding according to predetermined causal chains in time.

Bibliography :

• https://en.wikipedia.org/wiki/Mind%E2%80%93body_dualism

• Michel Weber and Anderson Weekes (eds.), Process approaches for consciousness in psychology, neuroscience and philosophy of mind (Whitehead Psychology Nexus

• Studies II) Archived on 2015-04-08 at Wayback Machine., Albany, New York, State University of New York Press, 2009.
  Lewis, C.S (1947). Miracles.

• "Causal determinism of quantum mechanics". Stanford Encyclopedia of Philosophy. Retrieved on November 16, 2012.
  -https://plato.stanford.edu/entries/dualism/

• https://www.allaboutphilosophy.org/cartesian-dualism-faq.htm

• https://www.iep.utm.edu/descmind/

• https://www.britannica.com/topic/Cartesianism