As it is known, Descartes is the founder of Rationalism and the methodology of this field. (1)
There was only one rule in Philosophy until rationalism: To think logically. It was the rule of Aristotle's logic. According to Aristotle, Intellect and thought are based on the rule of Logic.
The main principle of Logic was: Deduction and Induction, which means either reasoning using general rules or principles to form a judgment about a particular fact or reasoning using known facts to produce general facts or principles.
In Arabic, it is called "enfüs-ü âfak" which means to prove the general principles using the individual facts or to prove each fact using all the facts.
Another name for it is in French as "Subje and obje", which means "particle (piece, fragment) and whole ".
To think logically was the only rule of Philosophy from Aristotle until Descartes.
In other words, to imprison reasoning in the Rule of Logic and to refuse any thought that is against the rule of the Aristotle's Logic even though it is scientific. For example, if a scientist found out a fact as a result of his thoughts; and if it were proved to be right in practice scientifically, it would not be accepted as a thought unless it was done according to the rule of Aristotle's Logic by the philosophers and by the supporters of the Scholastic Theology (kelâm), which is accepted as a kind of philosophy in Islam. Rationalism is very strict. The Logic of Aristotle is the rule that cannot be given up by them so everything is based on it.
(1) Rene Descartes (1596-1650): He is a famous philosopher and scientist. He claimed that in order to reach the real knowledge, one should be suspicious of everything. He summarized his ideas saying, "I think, therefore I am." Descartes accepts that the concept of God has existed in our minds since we were born just like the principles of mathematics are based on. According to him, it is impossible to comprehend and understand such an excellent Existence with the sensations of man who is not perfect. *By this way, he believes in the reality of such an Existence who has been present in our minds since we were born. (The Encyclopedia of Life, the article about Descartes)
Descartes also founded the methodology and accepted it as the basic rule of thought that means thinking systematically. He put forward the rule of analysis and synthesis instead of induction and deduction. (2) Analysis, here, means dividing something into its separate parts and synthesis is combining the separate things into a complete whole. In Arabic, it is called as "tahlil and terkib" which means combining separate parts and re-separating the combined parts.
Thus, the Philosophy, developed according to the Logic of Aristotle during the Abbasids, passed to Europe after the 12th century. The Philosophy of Systematic Reasoning of Descartes took its place after being dominant for two or three hundred years. We see that there is no difference in principles between the Logic of Aristotle and the Methodology of Descartes when we study them.
Methodical reasoning followed logical reasoning and then Rationalism started after Descartes instead of the study of Philosophy. Philosophy and Rationalism helped physical sciences in many ways: They supported experimental science, speeded up the functions of the laboratory researches and caused the rising of today's technology presented to humanity. The origin and essence of the objects and the elements of which they are consisted is learnt by analyzing matter in this way. Chemistry, Physics, Medicine, Arithmetic have developed by means of it and it is called"Positive Science" in the literature of the World's Science, which means real and definite experimental knowledge.
It is true that the Logic of Aristotle and Philosophy which was developed during the Abbasids by the Islamic philosophers and by the Scholastic theologians depending on it, and the scientific discoveries due to them as well as the Methodology of Descartes in the developing branches of Science, provided a great supplement in today's Positive Science. This is true! The main reason of the great development of today's technology is the principle called as "analysis and synthesis" and introduced by Rationalism.
However, if we use and apply the principle of "analysis and synthesis" to Mind and Philosophy, we put the intellect in the inconvenience of the laboratory experiment same as the principle of logic that belongs to “the Logic of Aristotle” forces the intellect.
(2) Rene Descartes, "Discourse de la methode" (Speech on the method)
This makes the free thought of Intellect to be limited by the strict rules of Logic and Methodology because reasoning according to Logic and Methodology and calling it as Rationalism and Logic means to inconvenience the Intellect and thought. Unfortunately, Rationalism has dominated philosophy and mind for years in Europe and “metaphysical” realities are tried to be explained according to the principles of Logic and Methodology due to it.
Yet, human mind (Intellect) can only think about and search the physical world. It is able to solve the realities of the physical world only and it has been continuing to solve them.
It is impossible for the intellect to solve the Metaphysical (Spiritual) Realities on the point of which the physical world ends. It has not solved them so far because Intellect has a capacity, a limit. It does not have the power of understanding and solving the infinity or metaphysics.
Kant, (3) who noticed this inconvenience of Intellect, started to examine particularly the intellect itself and he made a critic of it. After Kant, a new way of thinking began in Philosophy and the idea “Intellect can solve everything" was given up. The strict Rationalism was made such a taboo that it was claimed that there was no other means of reasoning except Intellect to know the realities. Just at this point, Kant criticized Intellect and said that Reasoning could not solve the Philosophical realities of Metaphysics, and Intellect was unable to solve the “Absolute Truth”. He added that a great deal of facts would remain as “mysteries” for the Intellect.
(3) Immanuel Kant, (1727-1804): He is a well-known German Philosopher. He completed his first book called "the Critique of Pure Reason" in 1781. It is accepted as the most important philosophy book in the last two hundred years. (Encyclopedia Life, from the article about Kant)
The metaphysical realities are the essence, the origin of the Creation (nature and all the objects), the description of the inner world (metaphysical world), the Angels, Spirit, Paradise etc. It is a fact that it is impossible to comprehend and solve all these realities using the partial intelligence and the partial intelligence confuse reasoning and cannot exceed the guesses and hypothesis in spiritual and metaphysical matters and this will force and confuse mind as well.
In Europe, this strict and extreme Rationalism have been prevented by Kant with "The Critique of Pure Reason" and by Hegel with his "Scientific Dialectic".
Rationalism is valid until where the matter ends. Intellect has no right to mention metaphysics. It is about time we explained it as follows: (4)
Intellect is able to solve and has been solving everything, which is material-physical. It has the capacity of understanding, solving and explaining the subjects about the visible world whereas it cannot reach a definite judgment and knowledge in metaphysical matters.
Intellect is unable to know the concepts and qualities of the Metaphysical realities such as Spirit, Angels, the Heavens etc. as well as God and His attributes. It cannot solve the Absolute Truth because God did not give this power (capacity) to human mind (the partial intelllect that human beings have). Because of this, He sent His “Divine Message” to human beings so as not to be deprived of the spiritual knowledge and to know “His Existence with His attributes and the metaphysical World”. He assigned this duty to the Perfect Man who bears the Holy Spirit and who were called as "Great Mystics or the Devout ".
(4) For further information see also "Islâm'da Mezhepler ve Yükseliş (Religious Sects in Islam and Ascending)" (The chapter about Sufism, Theology and Philosophy in Islam" 1988- İzmir, distributed by Doğan Distribution in Malatya-Türkiye
Those who bear this Holy Spirit are also named as "Prophet, Messenger, Apostle, Wali - “the Friend of God- and guide". (5) God sends His Divine Messages by means of these great people and informs us about the metaphysical realities. When these divine messages and books are studied and read, we meet very important opinions and facts. We come across very important subjects about the physical and metaphysical worlds in the Koran, in the Bible (Gospel, the Bible), in the Torah and in the Psalms of David (Zabur). We also receive "Divine Messages" from the Disciples and Islamic Sufis apart from 28 Divine Messengers. (6) We should not ignore the poems, the wise sayings and the writings of some Christians Mystics and Islamic Sufis about the origin of the Creation and metaphysical subjects.
None of the philosophers considered the book "Füsus ül Hikem (The Bezels of Wisdom)" written by Muhyiddin-i Arabi as unimportant. Ibn-i Arabi is also an extreme Divine Messenger. He did not accept the role of Mind (Logic, Intellect) on Metaphysical subjects but he constantly emphasized that only the Intellect, which had a contact with the Universal Intellect or the person who had the Holy Spirit, could solve these realities. All the Sufis and Muhammad Ghazzali (7), who used to be a philosopher but then he chose the path of Sufism, claim that Metaphysical realities can never be solved with Methodology, Intellect and Logic without the role of the Holy Spirit.
Some of the Western philosophers agree with it. They accept and confirm that the mysteries of nature have not been solved yet and it is impossible to solve them using the partial intellect, and the Absolute Truth cannot be learnt with an ordinary mind. Descartes also accepted it.
The fanatic supporters of Aristotle Logic (Aristotle Logicians) and Descartes Methodists (who are called as rationalists in the Literature of Philosophy) are more rationalistic than Descartes used to be.
(5) "The Spiritual guide who is the Friend of God (Wali)" (Al-Kahf, 17)
(6) See: 28 Prophets mentioned in the Koran,
(7) See: "El Minkuzu min ed Dalâl-From Corruption to the Spiritual Guidance”
Descartes, who founded the Method of Rationalism, accepted that the metaphysical realities, the Reality of God and the Absolute Truth could not be solved with this practical intellect. (8)
Those extreme rationalists claim that all the physical and spiritual theories and principles as well as “the Absolute”Truth can be known with the partial intellect and they say that there is no other way of learning the physical and metaphysical realities except using Logic and Intellect.
What they want to do is; They try to convince that spirit does not exist, there is no reality that the Holy Spirit knows and there cannot be any Divine messages. They deny the Prophets who are the Divine Messengers, the books of God and also the opinions, ideas or the knowledge of the Great Scholars and of the Religious Guides based on revelations and discoveries. They call all of them "dogma” and ignore them. They refuse all the Divine Messages and the knowledge in the Holy Books or in the books of Sufis even though they are scientific and in accordance with science, practice and intellect. They cannot be "rationalists". Those who understand "Rationalism" in this way are the "materialists" who deny God, the Holy Messages of God (Divine Words and Divine revelations) and also the Prophets together with the Scholars of Sufism who are also the Divine Messengers.
They are particularly the simple materialists who are the noisy advertisers of “Rationalism” in Türkiye. The materialists who study and read a great deal are not as rationalist as they are because they are at least fair to say openheartedly that the Holy Books and the works of Sufis contain interesting ideas and scientific subjects. On the contrary, the simple materialists who chew the word "rationalism" in their mouth like a gum keep saying: rationalism, rationalism, rationalist…, but then they utter no reasonable word or write any books. The only thing they do is to repeat the word rationalism at the beginning of their sentences. They are the creatures whom Ziya Pasha described as: "Lots of fools who think they are clever." (9)
(8) See the six metaphysical opinions of Descartes
(9) A lot of fool, who think they are intelligent: Rationalists
These simple materialists confuse Intellect with Rationalism and cause an agitation of concepts. According to them, you refuse Intellect if you are not a rationalist in all the matters. In fact, rationalism is an expression used after Descartes and it is the Methodology of Descartes, which means thinking systematically in every subject. They are the Cartesians, even more Cartesians than Descartes himself, who claim that all the realities of Physical and Metaphysical matters and the Absolute Truth can be solved with this partial intellect.
They are the keen supporters of the Doctrine of Descartes same as the old Aristotle Logicians, who used to be more logical than Aristotle was.
The Koran, Sufism and all the Divine Messengers say that the partial intellect is able to solve the Physical Realities but Metaphysical Realities can only be learnt with the "Universal Intellect-The Spirit". The Koran explains this matter very clearly in the sixth verse of Chapter "Rum":
"That is God's promise; God will never break His promise. Yet, most men do not know it.” Most men (who have the partial intellect) know of the visible part of the life of the world (the physical part of the Creation).Yet, they are unaware, heedless, ignorant about the other world (metaphysics).”
The above verse clarifies the Intellect in man. Allah explained everything in the Koran and revealed His Divine message to the Prophet Muhammad, who is the writer of the Koran, and this great Divine Messenger transmitted this reality to humanity.
Every fair person should feel at least a little respect for the Prophet Muhammad when this verse is read and studied carefully. (10)
(10) See Muhammad -Jesus -Adam