Philosophy of Being and Knowledge

Epistemology (Philosophy of Knowledge)

Rationalism

Rationalism is a theory of knowledge asserting that reason is the source of knowledge. Rationalists observed that there is no direct link between what one observes and what one knows. For example, it is well-known that all crows are black, yet no one has ever seen all the crows that have lived, live, or will live. Thus, no one has experience of all crows, but everyone possesses knowledge about all crows. Similarly, no one has tested the electrical conductivity of all copper, but it is known that all copper is conductive; no one has observed the effect of gravity on every object, yet it is known that universal gravitation is a natural law. Hence, the question arises: from where does universal knowledge come? This question became a central issue in epistemology, dividing the philosophical community into various schools. Philosophers who believed that objects of knowledge do not generate knowledge about themselves are called rationalists. This term comes from the Latin "ratio," meaning reason. The name "rationalism" indicates that followers of this school recognize reason itself as the source of knowledge. The assertion that knowledge is formed by reason independently of experience led to the new problem of explaining how reason generates knowledge. While all rationalists agree that reason generates knowledge, they differ on how reason accomplishes this.

The most systematic and refined rationalist theory of knowledge was proposed by the eminent ancient Greek philosopher Plato (427-347 BCE). Plato began his reflections with the premise that everything that exists is created according to a specific plan. A watchmaker, before making a watch, has a design for how the watch should look; a builder constructs a house according to an architectural plan. If everything that exists is an embodiment of some plan, then the world, as it is, must be an expression of its grand design. Plato asserted that the world is an expression of designs he called Ideas. Ideas are pure forms. Everything that can be said about a thing is an Idea. For example, when someone describes a table, they mention that it is rectangular, has legs, and certain dimensions. Plato referred to all these features as Ideas because, before they were incorporated into the table, they appeared in the mind of the craftsman who created the table's design. The task of knowledge is to discern these Ideas.

Plato believed that the world is an embodiment of eternal and unchanging forms—Ideas. The world is created in their likeness. Knowledge is the reflection of Ideas in the mind. In his theory of knowledge, Plato sought to explain how the mind perceives Ideas. In his doctrine of the human being, Plato posited that the essence of a person is their soul. Human souls have eternally existed in the world of Ideas, having the ability to contemplate them. However, having diverted from the contemplation of truth, souls became detached from their purpose and fell into material bodies, which became their prisons. This detachment from the world of Ideas led to forgetfulness and confusion of knowledge. Thus, a person, upon birth, possesses all possible knowledge, as they have contemplated Ideas, but this knowledge is only implicit (unexpressed). To make this knowledge explicit, it needs to be revealed, which happens through experience. By seeing the things of the world, people recall the Ideas, as things are nothing more than reflections of Ideas, created in their likeness.

Thus, Plato believed that knowledge is present in the mind prior to encountering experience. Experience does not generate knowledge but only helps to reveal it. This is how Plato addressed the age-old epistemological problem: how is it possible for the mind to possess general knowledge while observing only particular facts? For example, a person sees that a rectangular table before them has four sides but knows that any rectangle has four sides. Plato believed this is possible only because the table is not the source of knowledge about rectangles. The mind possessed knowledge about rectangles even before the eyes saw the table, but the table helped to recall and organize that knowledge.

Therefore, Plato maintained that the knowledge a person has is a priori. The Latin "a priori" means "from the first" or "preliminary." From this term comes the concept of "a priori knowledge," which is knowledge that the mind possesses before encountering experience. Its opponents claimed that human knowledge is a posteriori. The Latin "a posteriori" means "after." A posteriori knowledge is that which the mind acquires as a result of encountering experience. Rationalists asserted that all human knowledge is a priori, while their opponents (empiricists) believed that all human knowledge is a posteriori, i.e., acquired after and due to experience.

A significant contribution to the development of rationalist epistemology was made by St. Augustine (354-430), a prominent Christian theologian and philosopher who bridged Antiquity and the Middle Ages. Augustine, as a Christian and a Platonist, sought to interpret Plato's philosophical theories in a Christian context. As a Christian, he believed that humans were created by God as a unity of body and soul and could not agree with Plato's notion that the human soul existed in the world of Ideas before entering the body, but he also did not wish to abandon Platonic rationalism. Augustine's solution to this dilemma was the development of the theory of illumination. The commonly accepted name of this doctrine comes from the Latin verb "illuminare," meaning "to illuminate." In this sense, illumination should be understood as enlightenment. Augustine believed that God illuminated the human soul, instilling in it all possible knowledge, which, however, remains in an implicit form. The task of the person is to reveal the knowledge granted by God through learning and intellectual effort. Thus, according to Augustine, humans possess a priori knowledge before encountering experience, and experience and learning merely help to actualize this knowledge.

Augustine’s theory of illumination provided the foundation for the eminent medieval thinker, Archbishop Anselm of Canterbury (1033-1109), to formulate his religious philosophy. Anselm’s primary concern was the proof of God’s existence. He is remembered in the history of philosophy for his development of the ontological argument. Anselm argued that since the concept of God exists in the human mind and this concept is shared by all people, regardless of religion or culture, and since this concept of God could not have been derived from experience—given that one cannot observe God in the surrounding world—the only way such a concept could be acquired is through illumination. God Himself implanted the concept of Himself into the human soul, thus knowledge of God is a priori.

This idea resonated with renewed vigor in early modern philosophy. René Descartes (1596-1650), a French philosopher who is rightly regarded as the father of modern philosophy, sought to find the foundation of certain knowledge. Mathematics, which provides absolute and indisputable knowledge, served as his model. For other realms of knowledge to produce equally reliable insights, they must be based on the same principles as mathematics. The foundation of mathematics is axioms—self-evident truths that require no proof. Descartes aspired to discover similar axioms for all knowledge. He thus faced the task of finding what is so evident that it admits no doubt. Descartes concluded that there is nothing in the world about which one could not doubt. Therefore, one is faced with two options: either accept everything as it appears or doubt everything. The first option is untenable, as seeing the world does not necessarily mean the world exists. Descartes proposed that what one observes might be a dream or an illusion cast by an evil demon. If there is no reason to trust what is seen and heard, then the only appropriate response is doubt. Thus, doubt became the axiom Descartes sought to base all knowledge upon. If doubt can be cast upon everything, then doubt itself is what cannot be doubted. It serves as the starting point of Descartes' philosophy. Since doubt is an evident fact, thinking is also a fact, as doubt is a form of thinking. If there is thinking, then there is someone who thinks, that is, a person. Descartes proclaimed: Cogito ergo sum (I think, therefore I am).

Thus, Descartes demonstrated the existence of the self through doubt. The next critical question for Cartesianism was the existence of God and the world. In his arguments about God, Descartes reiterated Anselm’s ontological proof. Since a person has the idea of God in their mind, and this idea could not have been acquired from the world, it must have been implanted by God Himself. Thus, knowledge of God is a priori. According to Descartes, God is not only the source of knowledge about Himself but also the guarantor of the truth of knowledge about the world. If God exists and is the creator of the world and humanity, it means He is also the source of human knowledge about the world. God created both the person and the world in such a way that humans can rightly understand the world. Since God is good, He does not deceive humanity. Without God as the guarantor of the truth of human knowledge, one would lack certainty about the truth of their knowledge.

Therefore, in Cartesianism, the source of true knowledge is God, who does not deceive humans but provides the means for genuine understanding. Cartesian rationalism became the dominant philosophical position of the early modern period until the Enlightenment. Descartes' ideas were echoed in various forms by Benedict Spinoza, Nicolas Malebranche, Gottfried Wilhelm Leibniz, and others. Throughout the history of philosophy, rationalism has been and remains one of the leading theories of knowledge, inspiring thinkers and scholars across the ages.