DESCARTES (1596-1650)
René Descartes is a French philosopher. The main subjects he worked on were the certainty of our knowledge and the relationship between the body and the soul. His book "Discours de la méthode" (Discourse on Method) is the work in which Descartes puts forward his philosophical thought. In his book "Meditiones de Prima Philosophia" (Thoughts on the Principles of Philosophy), he explains his thoughts on existence, knowledge and the existence of God. His book "Principia Philosophiae" (Principles of Philosophy) summarizes his philosophical system. The Cartesian coordinate system (the plane using the x and y axes) is one of his most important mathematical inventions.
Descartes, a methodological skeptic, aimed to bring the certainty in mathematics to philosophy. Man had two faculties; intuition and deduction, which allows us to derive new truths from clear truths known through intuition. In order to reach certain knowledge; He proposed a four-step path that can be summarized as not accepting anything we do not know clearly as true, dividing the problem into as small pieces as possible, examining these pieces in order from simple to complex, and frequently going back and reviewing the data obtained.
First, Descartes, who doubted everything, thought that he could not doubt that he was thinking at least and accepted his own self's knowledge as intuitively clear and distinct; "I think, therefore I am". Based on this relationship with his own self; he decided that the knowledge of the existence of God, who puts the knowledge of his own existence into our minds, mathematical information that is clearly given to our minds and is true because God cannot be deceiving, and thirdly, the knowledge we receive about the external world through sensations, which we tend to attribute to the activity of material causes (and God gave us this tendency), are valid. He became the founding father of subject-centered modern philosophy.
God is an infinite substance. Spirit and material substances are finite substances, having taken their source from God. Descartes is a dualist thinker because he divides the things created by God into two as spirit and matter. The interaction of spirit and matter occurs in the pineal gland in the human brain.
Form, size, dimensions, and mobility are the primary qualities of material substance, while features such as color, sound, taste, and temperature are secondary qualities. When God created nature, movement was added to the material substance, and now without his intervention, nature is a machine whose movements are all mechanical. Three laws of motion prevail in all nature; a thing continues to be at rest or in motion unless it is affected by something else, every moving object tends to continue its motion in a straight line, if an object encounters a stronger moving object, it changes its direction under the influence of that object, and if it is in a stronger motion, it moves that object along with itself. In his ethics,
Descartes advises to submit to the laws, customs, and religious beliefs of the nation, to remain loyal to one's convictions, to be determined in the course of action you choose, to adapt oneself and one's passions to one's environment and fate, to carefully choose the life pursuit that will be best for you, and defends freedom of will.
GEULİNCX (1624-1669)
Arnold Geulincx is a Dutch philosopher and logician. He tried to solve the relationship between the mind and the body. According to him, the reason that creates a movement in the body is not external stimulation or internal desire, but God. God creates a movement in the body through stimulation and desire. This view is called occasionalism. Geulincx says that we can only reach spiritual serenity by devoting ourselves to God.
MALEBRANCHE (1637-1715)
Nicolas Malebranche is a French philosopher. He tried to reconcile Augustine and Descartes. According to Malebranche, who said that there is no interaction between the soul and the body, but a parallelism (psychic-physical parallelism), our will is only an occasion. Everything in the universe is due to the will of God.
SPİNOZA (1632 - 1677)
Baruch Spinoza is a Portuguese-born philosopher of Jewish origin. In his book Theological-Political Treatise (Theological-Political Treatise), he explains his thoughts on prophecy, prophets, the holy book, the relationship between philosophy and theology, and the foundations of the state. In his book Ethica (Ethics), he provides in the form of definitions, axioms, propositions and proofs,a comprehensive review of God, mind, emotions, human freedom, metaphysics, epistemology, psychology and ethics.
Spinoza is against dualism, accepts God as a single substance, and is pantheist. Soul and matter are two of God's infinite attributes. The soul's modus (determination) is thinking, the body's modus is space. All thought-about thoughts belong to God or nature, the laws of nature are the internal cause of everything. Determinism prevails in nature, that is, everything in nature necessarily happens.
There are three groups of knowledge; sensory knowledge, scientific knowledge based on common concepts formed by the mind, and intuitive knowledge (divine, complete knowledge). Mental and physical events develop parallel to each other (psycho-physical parallelism).
Accepting the world as it is, not being a slave to our passions, and the love of God reached through intuitive knowledge lead us to true happiness. The source of the social contract is the human instinct to survive. The best government is democracy. He argues that religious authority should have no role in a secular, democratic state.
LEIBNIZ (1646-1716)
Gottfried Wilhelm Leibniz is a German philosopher. He thinks that philosophy should be expressed in a mathematical language that has a high value of accuracy and precision He classifies propositions into two groups of truth as rational truths and factual truths. Rational truths are necessary truths that are inherently present in the mind, thinking the opposite of these leads the mind into contradiction. Factual truths are acquired through experience, they are contingent, thinking the opposite of them does not lead the mind into contradiction, the condition of truth is the principle of sufficient reason.
The basic unit of everything in the universe is the monad, which is a simple substance. Monads, which are spiritually constructed, cannot be divided and are not extended. Even the founding monads of matter are spiritual. The harmonious functioning of the soul and body is a principle established by God. While Leibniz argues that free will exists, he also says that God has determined everything in advance.