Philosophy of Being and Knowledge

Epistemology (Philosophy of Knowledge)

Empiricism

The rationalist stance of Plato was met with ambivalence even in Antiquity. His student, Aristotle (384-322 BCE), approached his inquiries not from general ideas, as Plato did, but from individual things and substances. While Plato analyzed general ideas first and then things, attributing the source of knowledge to the intellect that perceives these ideas rather than to experience, Aristotle began with individual things, viewing them as the source of knowledge. However, Aristotle believed that experience only provides the material from which the intellect constructs knowledge. Experience becomes knowledge only when transformed into general concepts. Thus, Aristotle focused on how the intellect converts experiential data into knowledge and how it operates with concepts, leading him to prioritize logic over epistemology. No other genius has contributed as much to the development of logic as Aristotle. In epistemology, Aristotle elevated experience to the pedestal of the source of knowledge.

Medieval philosophy sought to anchor ancient philosophy within a Christian framework. Given that Plato and Aristotle were the greatest thinkers of Antiquity, their ideas set the tone for medieval philosophical discourse. Augustine introduced Plato into Early Medieval thought, and it was through Augustine’s interpretation that Platonic philosophy became rooted in European thought. In the High Middle Ages, Aristotle’s philosophy gained prominence, with Thomas Aquinas (1225-1274) emerging as the key figure who secured Aristotle’s central place in European philosophy. Following Aristotle, Thomas regarded experience as the source of knowledge. What one sees and hears enters the intellect, is processed, and transformed into knowledge. Thus, Thomas asserted, “Nothing is in the intellect that was not first in the senses.” This position prevailed in the epistemology of most High Medieval philosophers due to Aristotle’s undeniable authority and influence during that period.

During the Renaissance, debates about the nature of knowledge continued. This era sought a return to classical standards, and since High Medieval philosophy had been dominated by Aristotelian schools, Plato became more prominent in Renaissance philosophical discourse as his ideas opposed those of Aristotle. However, Plato’s dominance was not absolute. Sir Francis Bacon (1561-1626) emerged as an opponent of contemporary rationalism, arguing that science, regarded as the most perfected form of knowledge, should employ two methods: a destructive one to cleanse knowledge of distortions and a constructive one to derive new knowledge from experience and synthesize it through induction. Bacon thus championed empiricism. The term "empiricism" derives from the Greek "ἐμπειρία" (experience). Empiricism is an epistemological approach that posits experience—what one observes—as the source of knowledge.

In the Early Modern period, Cartesian rationalism was the dominant philosophical school, with its rationalist theory of knowledge. The Enlightenment emerged as a response to the major philosophical systems of the time, particularly Cartesian rationalism. Most Enlightenment philosophers were empiricists. The most comprehensive empiricist theory of knowledge was developed by the English philosopher John Locke (1632-1704). He argued that experience is the source of knowledge, but he interpreted experience broadly, encompassing both external (e.g., sight, hearing) and internal (e.g., spiritual) experiences. These two types of experience yield two forms of knowledge: knowledge derived from external experience is through sensations, while knowledge from internal experience is through reflections. What experience fills the mind with, Locke called "ideas." Locke’s concept of "ideas" differed from Plato’s, where ideas are the archetypes of things, eternal and independent of the knower. For Locke, ideas are knowledge about things that arise from cognitive activity. Ideas, according to Locke, can be primary or secondary. Primary ideas reflect states of affairs independent of the perceiver, such as the square shape of a table, while secondary ideas reflect states that arise only during contact with the perceiver, such as tastes, which appear only when a substance touches the taste receptors. Locke also distinguished between simple and complex ideas. Simple ideas are direct reflections of experience, while complex ideas are constructs of the mind resulting from the processing of simple ideas. The mind can transform simple ideas into complex ones because it possesses the necessary internal faculties. Thus, Locke laid the foundation for empiricism in Enlightenment philosophy, imbuing the period with an empiricist spirit.

The principal problem that any strand of empiricism must address is the central paradox of knowledge: how can general knowledge arise when humans experience only particular facts? For instance, no one has ever seen all the crows that have lived, are living, or will live, yet everyone knows that all crows are black. In rationalism, Plato offered an answer to this question: the human intellect perceives not individual things but general ideas; hence, knowledge is general. Within the framework of empirical theory, Locke addressed this fundamental problem by phrasing it as follows: How can simple ideas be transformed into complex ones? This is possible because the intellect possesses the necessary faculties.

However, Locke's resolution of this problem could not satisfy all empiricists. Since natural faculties of the intellect cannot be observed in experience, some empiricists claimed there was no basis for asserting their existence. Critics argued that Locke had deviated from pure empiricism. Another Enlightenment thinker, David Hume (1711-1776), made a new attempt to solve this problem. Rejecting Locke’s faculties of the mind, Hume found himself needing to explain why the intellect transforms data about particular facts into general knowledge. Since no pattern observable in experience could account for this, Hume argued that no such pattern exists. Transforming particular facts into general knowledge is merely a human habit. Through habit, Hume explained all universals: morality, law, religion, and so forth are collective habits.

Nevertheless, Hume believed there are two realities one can know: relations among ideas and facts. Hume defined facts as everything observable in the external world. For example, “Copper conducts electricity” is a fact. Relations among ideas pertain to the realm of the intellect and need not be reflected in the world. For instance, “The square of the hypotenuse is equal to the sum of the squares of the other two sides” is a relation among ideas (hypotenuse and sides). Even if no triangular objects exist in the world, the Pythagorean theorem remains true. If a person can have true knowledge of something that does not exist in the world, it suggests that eternal truths exist independently of experience.

The extreme form of empiricism is sensualism. The term derives from the Latin "sensus," meaning sense. Sensualists argued that the only way to acquire experience is through sensory perception. While Locke posited two types of experience—external and internal—sensualists denied the possibility of internal experience. Humans have five senses (sight, hearing, taste, smell, touch), and these five senses are the sole means of knowledge. The most prominent sensualist theory of knowledge was formulated by the Catholic priest and philosopher of the French Enlightenment, Étienne Bonnot de Condillac (1715-1780). He believed that the intellect is merely the processing of sensory data. Sensory organs perceive information, which the intellect then memorizes, compares, and analyzes. Based on this, Condillac argued that if a statue had at least one sense (e.g., smell), it would receive different data, compare them, remember, and analyze them. Thus, the statue would possess intellect. This comparison entered philosophical discourse as the "statue of Condillac." He drew this idea from the early Christian philosopher Arnobius. If knowledge is only possible through the senses and the task of philosophy is to study knowledge, then, according to Condillac, for philosophy to be scientific, it must become psychology.

Various forms of empiricism continued to develop in the subsequent centuries. However, they were, to some extent, repetitions of the types of empiricism proposed by Locke, Hume, or Condillac. The main distinction between rationalism and empiricism lies in their different understandings of the nature and origin of knowledge. Empiricists believe that the source of knowledge is experience, and that the human mind, at birth, possesses no knowledge. It is a tabula rasa (blank slate), and the entire course of a person’s life, accompanied by cognitive activity, is the recording of new information on this slate. Thus, throughout life, a person accumulates knowledge. All knowledge is a posteriori, meaning acquired after and as a result of experience. Rationalists, on the other hand, believe that a person is born with innate knowledge, which, however, is implicit and requires intellectual effort to become actualized and manifest.