1. Origin of Cognition

Empiricism holds that all knowledge is obtained from one’s experience, whereas rationalism claims that true cognition can be gained only through the operation of one’s reason, independently from experience. During the seventeenth and eighteenth centuries, empiricism was advocated in Great Britain, and rationalism was advocated in continental Europe.

1.1. Empiricism

a) Bacon (1561-1626)

Francis Bacon established the foundation for empiricism. In his renowned work, Novum Organum (1620), he considered traditional learning to be merely a series of useless words, empty in content, and that correct cognition is obtained through observation of nature, and experimentation. According to him, in order to obtain correct cognition, one must first renounce one’s pre-conceived prejudices. As prejudices, he listed four Idols (idola).

The first is the Idols of the Tribe. This refers to the prejudice into which people in general are likely to fall, namely, the prejudice whereby the real nature of things are reflected distortedly, because the human intellect is like an uneven mirror. An example is the inclination to view nature as personalized.

The second is the Idols of the Cave. This prejudice arises due to an individual’s unique nature, habits, or narrow preconceptions as if one were looking at the world from inside a cave.

The third is the Idols of the Market Place. This refers to the kind of prejudice that derives from one’s intellect becoming influenced by words. For example, words may be created for things that do not exist, which could lead to empty arguments.

The fourth is the Idols of the Theatre. This is the prejudice that arises from blindly accepting authority or tradition. In other words, it is the prejudice that arises from relying on an authoritative thought or philosophy.

Bacon said that we should first remove these four Idols, and then observe nature to find the essence within each individual phenomenon. For that end, he proposed the inductive method.

b) Locke (1632-1704)

John Locke systematized empiricism, and in his major work, An Essay concerning Human Understanding, he developed his views. Locke denied what Descartes called “innate ideas,” and considered the human mind to be like a blank sheet of paper (tabula rasa): All the ideas coming into the mind are drawn on the blank paper of the mind just as a picture or letters are drawn on a white paper. Thus, all ideas come from experience. ²

Ideas come into the mind from two sources: one source is sensation, and the other is reflection. For Locke, experiences through sensation and reflection are the origin of cognition. Sensation refers to one’s ability to perceive external objects through one’s sense organs. The ideas of yellow, white, hot, cold, soft, hard, bitter, sweet, and so on, derive from sensation. Reflection refers to our perception of the operations of our mind such as thinking, doubting, believing, reasoning and willing.

Ideas consist of “simple ideas” and “complex ideas.” Simple ideas are those obtained individually and separately from sensation and reflection. When simple ideas become higher ideas through combination, comparison and abstraction under the operations of our understanding, they become complex ideas.

Simple ideas include those with objective validity, namely, solidity, extension, figure, motion, rest, number, and the like; in addition, simple ideas include qualities with subjective validity, namely, color, smell, taste, sound, and the like. The former qualities are called “primary qualities,” and the latter are called “secondary qualities.”

There are three kinds of complex ideas, namely, mode, substance and relation. Mode refers to an idea expressing the state or quality of things, that is, the attributes of things, such as the mode of space (distance, immensity, figure), the mode of time (succession, duration, eternity), the mode of thinking (perception, recollection, contemplation), the mode of number, and the mode of power. Substance refers to an idea concerning the substratum that carries the various qualities. Finally, relation refers to the idea that comes into being by comparing two ideas, like the ideas of cause and effect, identity, and diversity.

Locke regarded knowledge as “the perception of the connection and agreement, or disagreement and repugnancy of any of our Ideas.” ³ He also said, “Truth is the marking down in Words, the agreement or disagreement of Ideas as it is.” ⁴ He sought to answer the question concerning the origin of cognition by analyzing ideas.

Locke considered certain the existence of the spirit, which is recognized intuitively, and the existence of God, which is recognized through logical proof. But he considered that there can not be certain regarding the existence of material things in the external world, because they can be perceived only through sensation.

c) Berkeley (1685-1753)

George Berkeley rejected Locke’s distinction between primary qualities and secondary qualities, and described both primary and secondary qualities as subjective. For example, distance seems to exist objectively as extension; namely, it seems to be an idea of the primary qualities. According to Berkeley, however, it is a subjective idea. The idea of distance is obtained as follows. We perceive a certain object from a distance with our eyes, and then we approach it and touch it with our hands. When we repeat this process, a certain visual sensation leads us to expect that it will be accompanied by certain tactile sensations of walking. Thus arises the idea of distance. In other words, we do not look at distance as extension itself.

Locke affirmed substance as being the carrier of qualities, but Berkley rejected this view and instead, viewed things as being mere collections of ideas. He asserted that “to be is to be perceived” (esse est percipi). Thus, Berkeley denied the existence of the substance of material objects, but he had no doubt as regards the existence of spirit as the substance that perceives.

d) Hume (1711-76)

David Hume developed empiricism to its logical conclusion. He considered our knowledge as being based on “impressions” and “ideas.” An impression is a direct representation based on sensation and reflection, whereas an idea is a representation that appears in the mind through memory or imagination, after the impression has disappeared. Impressions and ideas make up what he called “perceptions.”

Hume enumerated resemblance, contiguity, and cause and effect as the three laws of the association of ideas. He held the cognition of resemblance and of contiguity as being certain and posing no problem, but there is a problem with cause and effect, he said.

With regard to cause and effect, Hume gave the following example: when one hears thunder after a bolt of lightning, one usually thinks that the lightning is the cause and the thunder the effect. Hume, however, claimed that there is no reason to connect the two as cause and effect, for they are merely impressions; the idea of cause and effect is established on the basis of people’s subjective customs and beliefs, he asserted. As another example, the phenomenon of the sun rising shortly after a rooster crows is empirically well known. But we can not say that the rooster’s crowing is the cause, and the sun’s rising is the effect. Knowledge accepted as cause and effect is thus based on subjective human customs and beliefs.

In this way, empiricism, with Hume, became transformed into skepticism. Concerning the idea of substantiality, Hume, like Berkeley, doubted the existence of substance in material objects. He went even further by doubting the very existence of the spiritual substance, considering it to be nothing more than a bundle of perceptions.

1.2. Rationalism

In contrast to empiricism, which developed in Britain, and discussed above, rationalism expanded over continental Europe, represented by Descartes, Spinoza, Leibniz, Wolff, and others. Rationalism held that it is not through our experience that we can obtain correct cognition, but only through our thinking. Correct cognition can be obtained only through deductive logical reasoning. This is the position of Continental rationalism.

a) Descartes (1596-1650)

René Descartes, regarded as the founder of rationalism, began by doubting everything, as a method of obtaining true knowledge. This technique has been called “methodic doubt.”

Descartes believed that our sensations can deceive us, and so he doubted everything related to sensation. Why did he adopt such a method? He did so in order to obtain genuine truth. If there remains something that can not be doubted after we have doubted the existence of all things in the world and even ourselves, it is because it is indeed truth. Thus, he doubted everything. As a result, he came to realize that there is one thing which can not be doubted: the fact that I am engaged in the act of doubting. Hence, he established his famous proposition, “I think; therefore, I am” (Cogito, ergo sum). For Descartes, the proposition “I think, therefore I am” is the first principle of philosophy. ⁵ That proposition is certain, he argued, because one’s perception of it is clear and distinct. He then derived the general rule (the second principle) that, “things we perceive very clearly and very distinctly are all true.” ⁶

“Clear” implies that something is present and obvious to the spirit, and “distinct” implies that it is distinguishable from other objects. ⁷ The opposite of “clear” is “obscure,” and the opposite of “distinct” is “confused.” The existence of the spiritual substance, an attribute of which is thought, and the existence of the material substance, an attribute of which is extension, can be recognized as certain. In other words, the Cartesian dualism of matter and spirit is established from the first and second principles: The existence of mind (thought) is proved from the first principle, and the existence of matter (extension) is proved from the second principle.

In order to guarantee a clear and distinct cognition, one must not allow cases in which evil spirits secretly deceive people. In order to prevent such a thing, one must assume the existence of God. If God exists, no mistake can occur in our cognition, because the honest God can never deceive us. Descartes is said to have proved the existence of God as follows:

First, the idea of God is innate within us. In order for this idea to exist, the cause of this idea must exist.

Second, the fact that we, who are imperfect, have the idea of a perfect Being proves the existence of God.

Third, since the idea of the most perfect Being necessarily contains existence as its essence, the existence of God is proved.

In this way the existence of God was proved. Therefore, God’s essences, namely, infinity, omniscience, and omnipotence, become clear; honesty (veracity), as one of God’s attributes, is secured. Accordingly, clear and distinct cognition is guaranteed. Descartes ascertained the existence of God and the existence of spiritual and corporeal substance, or mind and body; among these, the only independent being, in the true sense, is God, for mind and body are both dependent on God. Descartes also held that mind and body―with the attributes of thought and extension, respectively―are substances independent from each other; thus, he advocated dualism.

Descartes proved the certainty of clear and distinct cognition, thereby asserting the certainty of rational cognition based on the mathematical method.

b) Spinoza (1632-77)

Baruch de Spinoza, like Descartes, thought that truth can be cognized through rigorous proofs, and tried to develop logical reasoning, particularly by applying the geometrical method to philosophy.

The premise of Spinoza’s philosophy was that all truth can be cognized through reason. That is, when one perceives things “in their eternal aspects” (sub-specie eternities) through reason and also perceives them wholly and intuitively in their necessary relationship with God, true cognition can be obtained. To perceive things “in their eternal aspects” means to understand all things in the process of necessity. Let me explain. When we look at things from such a standpoint, we need not be attached to or disturbed by transient things or passing phenomena, but rather we can come to comprehend things, phenomena, and even ourselves as being expressions of God’s eternal truth, hence, as precious things. Then, we can reach our perfection, and obtain true life, boundless joy, and true happiness. This is what is meant by perceiving things in their eternal aspects. Such perception can be obtained through clear and distinct reason and our spiritual sense.

Spinoza divided cognition into three types: imagination, scientific knowledge (which is on the level of reason), and intuitive knowledge. Among these three, he held that if imagination is not properly ordered by reason, it is imperfect. He thought that true cognition can be obtained through scientific knowledge and intuitive knowledge. For Spinoza, intuitive knowledge is not separated from reason, but rather it is based on reason.

Descartes considered mind, with thought as an attribute, and body, with extension as an attribute, to be substances independent from each other. In contrast, Spinoza held that God alone is substance; and that both extension and thinking are God’s attributes. Spinoza asserted that God and nature are in the relationship of natura naturans (the origin of all things) and natura naturata (everything which follows, by necessity, from the nature of God), and are inseparable. Thus he developed a pantheistic thought, claiming that “God is nature.”

c) Leibnitz (1646-1716)

Gottfried Wilhelm von Leibniz placed great importance on the mathematical method, and considered that the ideal was to derive every proposition from a few fundamental principles. He classified truth into two kinds: first, there is truth that can be arrived at logically through reason, and second, there is truth that can be obtained through experience. He labeled the former as “eternal truths,” or “truths of reason,” and the latter as “truths of fact,” or “contingent truths.” He held that that which guarantees truths of reason is the principle of identity and the principle of contradiction, and that which guarantees truths of fact is the principle of sufficient reason, which says that nothing can exist without sufficient reason.

Yet, such distinctions among kinds of truths apply only to the human intellect. This is because God can cognize, through logical necessity, even that which is regarded by humans as truths of fact. Therefore, ultimately, truth of reason was held to be the ideal truth.

Leibniz also held that the true substance is the “monad,” or a living mirror of the universe. He explained the monad as being a non-spatial substance having perception and appetite, whereby apperception arises as a collection of minute unconscious perceptions. Monads were classified into three stages: sleeping monads (or naked monads) in the material stage; souls (or dreaming monads) in the animal stage, possessing sensation and memory; and spirits (or rational souls) in the human stage, possessing universal cognition. In addition, there is the monad on the highest stage, which is God.

d) Wolff (1679-1754)

Based on Leibniz’s philosophy, Christian Wolff further systematized the rationalistic position. Yet, in the process of this systematization, Leibniz’s original spirit was lost or distorted, and so the main part of Leibniz’s theory is missing from Wolff’s system. Especially, the theory of monads and the doctrine of pre-established harmony were distorted. Kant belonged to the Wolffian school at first, but later strongly criticized him as representative of rational dogmatism. Wolff held that true knowledge is the truth of reason, derived logically from fundamental principles. He proposed that all truths be established solely on the basis of the principles of identity and contradiction. He accepted the existence of empirical truths as fact, but according to him, truths of reason have nothing to do with empirical truths, and empirical truths are not necessarily true, but only contingently so.

In this way, Continental rationalism attached little importance to the cognition of facts, considering that everything must be cognized rationally, and ultimately ended in dogmatism. ⁸