1. Introduction

1.1. Cartesianism

This classic philosopher by excellence, René Descartes (1596-1650) introduces a way of thinking, a point of view based on clear and distinct ideas, on the discharging of philosophical reflection of any authority (religious or political), thus establishing the tradition of a personal thinking practice. The French philosopher pointed out that this senses-based view is systematically susceptible to doubt, while the mathematical conception is certain, thus, a method is proposed to distance ourselves from the senses-based conception and towards the most objective one.

Metaphysical meditations (1641) [1] are another fundamental philosophical works of René Descartes. His idea starts with a methodological doubt that questions everything, thus discovering that in the extreme context of doubt we cannot doubt that we doubt.

René Descartes begins with his methodological doubt from the outer to the inner of what he had thought he knew until then, following a kind of spiral that wraps around himself as a thinker. He first doubts what he learned from books or from others; then doubts his own sense experiences [2,3]. Because these experiences are similar of those in dreams, we are only going to be wrong all the time. He doubts every-thing; there is nothing certain. This way he reaches the conclusion that there is some-thing he can certainly state without being wrong: "I doubt". There is no doubt that there is an "I" who doubts. Thus, "I doubt it, therefore I think" (Dubito ergo cogito). And one who thinks he exists. Hence, "I think, therefore I am" (Cogito ergo sum). It is an intuition and an immediate record of the mind. The one thinking has self-certainty. In doing so, René Descartes gains a leading position by asserting the solitary of the thinking one. We are dealing with a kind of skepticism focused on beliefs based on senses, a skepticism about their degree of objectivity, as the French philosopher shows is compatible with the possibility of natural science.

According to the French thinker, the world of vast reality, the outer world, is the realm of passivity: in the expanse, we only find outer motion, but never a spontaneous motion. A moving body push another, and so on. René Descartes' philosophy is a dualistic one: everything that exists comes down to two fundamental realities, irreducible in relation to each other: extension and thinking, res extensa and res cogitans. Mind is active and sets itself spontaneously in motion. Extension is passive; any motion is carried from the outside. Starting here Descartes derives two claims. According to the first, everything that is extended, nature, must be explained only by external relation-ships, by mechanistic theories, never by spontaneous motion, change, or by internal properties [4,5]. His claim remains valid even when it comes to living bodies. According to René Descartes' famous theory of the animal-machine, the body of the animals is extending, i.e., passive in its essence and subjected to the mechanical laws of motion. The human body is also of a mechanical nature. At the time, his theory certainly did a huge service to modern science, asking of it to admit only mechanical, clear and verifiable explanations. The second claim concerns res cogitans, thinking. What is spirit, what comes from thought is, in his eyes, pure depth and pure activity. Neither will nor intellect are ever set in motion from outside [6]. Thought and will claim their radical interiority and complete spontaneity. Symmetrical lysting mechanism, the voluntarism of the spirit is here affirmed. Such dualism is particularly problematic. René Descartes tries to solve it by resorting to the famous pineal gland, located at the base of the brain. It is here important not the reasons why the French philosopher chose this gland (it is unique in the brain and would not exist in animals, so there is no question of the body-soul relationship), but the fact that, by in-stalling the spirit (unknown to the expanse) in the expanse, and by including it in a system of mechanical movement, a special mononeistic conclusion is suggested to the Cartesian dualism. However, the question remains if two substances that are completely opposite can act on each other.

1.2. Cartesian Dualism

The clear distinction between mind and body, assumes that the mind is a kind of substance, and the body is another one. The French thinker announces that he is nature of a thought thing, explaining that by "thinking" he means any operation of the mind whose reality cannot be argued by the person of that mind. This property of being unquestionably real, directly accessible to self, is the defining property of the mind. Our mind is not so much human as finite, while God's mind is not so much superhuman as infinite. Human capacities are thus much more limited and constrained than of the divinity. René Descartes's distinction between purely intellectual capacities, on the one hand, and the capacities to imagine and feel, which involve the body, can be seen as a division of the capacities that we have in common with God and by which we can have something similar to His objective understanding of reality and those that we do not have in common with the divinity, which are not necessary for objective understanding [7]. The capabilities of the human mind are not in a natural order of the species, but in an order of perfect substances.

Philosophy means for René Descartes to ask metaphysical questions. First, a reliable foundation must be created, namely a common ground must be found that, like the axioms of mathematics, is clearly and crystal clear, and can therefore bear the whole construction of philosophy. Therefore, we must first destroy all provisional certain-ties, which has so far passed, as undoubted truth must be subjected to doubt, to a fierce skepticism. For this reason, René Descartes believes that it is his goal to demolish everything from the ground up, starting from the beginning, from the foundation. He assumes at any risk the freedom of thought that doubts. The intransigence with which it achieves this causes its doubt to produce the decisive mutation to modern philosophy, which, following René Descartes, is based on the subject and his freedom. When the rational philosopher begins to check the solidity of what has been considered certain in a self-evident way, he feels that everything is beginning to wobble. The motion of thought that leads here is one of the decisive turning points in the history of the hu-man spirit. Cartesian doubt rises the original certainty itself. Even though I can doubt everything I represent, any object I think I know, my representations of this object exist, and in this way, I exist, the one who has these representations. Doubting itself proves that I exist. For as long as I doubt it is a necessity that I, the one who doubts, to exist.

This certainty, the deepest of my existence, cannot be destroyed even by the idea that God can deceive me. Even if God deceives me, I still exist - I, the deceived one. With this skeptical attitude, René Descartes succeeds in paving the way for a new certainty. In the vortex of doubt, however, something remains indisputable: the fact of one's own existence. The fact that the French thinker no longer finds in God the place of the original certainty, as the philosophy of the Middle Ages has almost always done, but sets it into man, decisively marks his subsequent thinking. From now on, it will be up to modern philosophy to look at man, explicitly, in his autonomy and entrust him only to that certainty that springs from himself.

1.3. Rationalism and Skepticism

René Descartes forges a new image of reason, conquering, thus allowing us to rejoice and become masters of the existing ones. This way, the idea of conquering nature ap-pears as a major paradigm deeply related to the structure of modernity. René Descartes initiates a radical intellectual reform program, refusing to accept as true any sentence that could not be clearly proven. The whole science, he argues, must be based on metaphysics. The obvious truths in themselves are those that reveal themselves to the natural light of reason, the truth a priori. The first example of the obvious truth given by the French philosopher is the one contained in the famous cogito: "I think, therefore I am". I cannot doubt that I'm thinking, without confirming that I'm thinking. Any clear and distinct idea can be considered true. Clarity and distinctiveness are regarded by René Descartes as proving an intrinsic criterion of truth [8]. Ratio (rea-son), no longer cantoned in the universe of theory, soars towards the conquest of the cosmos. The contradictions of the age are assumed, on the one hand the objectivity of triumphant science and technique, on the other hand the subjectivity of the individual, self-discovery and, with it, the invention of skepticism. It is remarkable the terror etic lucidity to detach from any authority and to make this a first principle of knowledge. To capture certainty is also to express it clearly. In this way, European philosophy was forged to think in a modern language, being cleansed of scholastic and Renaissance preciousness. Philosophy becomes rigorous and clear, expressed unequivocally by concept, not by metaphor. It is a deliberate departure from the artistic ineffable and pathos. The construction of this rational, beautiful ideal system, beautiful through balance and clarity, was adopted as a model in classicism. Knowledge of intellect is one of the most important issues here. He is the only one capable of perceiving the truth. It is stipulated that the nature of matter must be completely intelligible; it cannot have any quality or take any form that is not clear to the intellect. Using a methodological synthesis between intuition and inference, the philosopher derived from the principle of cogito the existence of the material world. He did not want his metaphysical system to be independent of his research in physics, mathematics or psychology.

2. Cogito by Descartes

René Descartes is the metaphysicist who with his distinction between the soul, the thinking substance, and the body, the expanse substance, will address one of the greatest problems of classical philosophy. The key will not be anything but Cogito. The choice of Cogito as a prime principle can be considered the greatest idea of the French philosopher. Through this reflexive operation called Cogito, thinking absolutely and lawfully takes possession of a certain reality for the first time. This closeness is achieved in a whole new way, because, through skepticism, through doubt, the spirit has learned to move away from the senses, which previously provided him with his most emphasized beliefs and mingled in all his thoughts. One of the main merits that the thinker attributes to his meditations is to clearly demonstrate the real distinction between the soul and the body.

The Cartesian rationalism principle is based on the certainty that any spirit may achieve the knowledge of the truth. The mathematical model represents the ideal model for René Descartes, the ideal model that needs to be strived for.

3. Conclusions

The Through René Descartes, the autonomy of the self receives its first exemplary philosophical foundation. The discovery of self-certainty indicates the path that will later lead to the interrogation of the being of man, considering his distinction from things. The essence of the mind is thought and nothing else, thinking in broad sense including feeling and will, in short, the whole field of consciousness. This creates a gap that is difficult to cross between man as a thinking being and other unconscious and unthinking entities. Obvious dualist, the one, living only in consciousness, loses contact with things. With René Descartes begins the modern division of reality into subjects, on the one hand, and pure objects, on the other, a division that today still burdens reflections on man and the world [9].

René Descartes thus opened the royal path of all modern thought, his conception positioning man at the center of the whole context of social nature and political circum-stances. The double requirement, the mechanistic explanation for the extended sub-stance and absolute responsibility for the thinking substance, was so important for the French thinker that he sacrificed the coherence of his system [10]. On the other hand, the Cartesian system privileges the possibility of an immortal soul. Thus, the body belongs to the expanse and dissolves into it. The soul, as the pure depth of thought, does not fall apart with the body. In the treatise Discourse on the method (1637) – Discourse on the method of rightly conducting one’s reason and of seeking truth in Sciences [11] – are formulated the rules that must be applied to any research, philosophical or scientific. Starting here, the French philosopher will imply his existence (I Think, therefore I am) [11,12]. The existence of divinity arises from the notion of infinity within us. This rationalist doctrine is based on the use of reason in any circumstance.

We would like to express our own opinion starting from Decartes's theory, with practical applicability to clinical experience in the medical field and to a personal interpretation of what means possible and probably in medicine, with reference not to the principles of logic or mathematics, but to those of evidence-based medicine. Thus, all modern medical treatises, especially American ones, by which students are taught to think, describe a main diagnosis and more differential diagnoses. They are presented in a descending order of probability of occurrence. Personally, we believe that this approach damages clinical intuition and classical medical thinking developed by true practitioners, who did not have at hand neuroimaging tools or multiple blood tests, cephalo-radial fluid, ultrasounds or other systems ancillary to the mind, which some-times remain disparate in the thinking of the modern clinician. Doctors belonging to ancient generations relied on symptoms grouped into clinical syndromes, which de-fined the uniqueness of each practitioner, as well as the aura of imago and "semi-god". Thus, in medicine that was practiced about 20-30 years ago (before the proliferation of modern computer science techniques), it was possible more than likely. A good clinician, he could jump on the tree more possibilities and he could accurately go on clinical feeling, experience and detailed analysis through observation, percussion, listening directly to diagnosis. Sometimes, this circle of diagnostic tree can increase the hope of diagnosis about two months earlier, managing to save time in a serious illness. Decartes's concept of "I doubt and the only real thing is that I doubt" finds wide applicability in medicine, if the clinician's mind is in constant action, it moves into the "hem" of the diagnostic tree not according to probabilities, but to relevance, namely the concept of being possible. Apotheosis of the results of some devices short-circuits and, unfortunately, sometimes replaces the van that should remain permanently present in the mind of the specialist, which by which the accuracy of the modern medical act loses.

We can compare it to what Descartes named spatiality, which should be passive, if we interpret it in the medical realm as the corporality of the sick being, the place over which an outside action should happen, passive to the one in question.