| Part 1 The Theory of Faith | Hirohumi Hoshika |
To understand Kant's philosophy, it is necessary to understand the problems that Kant was trying to solve. The challenges faced by Critique of Pure Reason become clear by tracing from the philosophical trends of the 17th century to Kant's "pre-period critical" thought. (pre-period critical: before he wrote Critique of Pure Reason). For more information on this, please refer to Part 2 "The Theory of Faith and Reason" Chapter 4, which summarizes the general history of philosophy.
Here, I will summarize the philosophical solutions and their influences that Critique of Pure Reason attempted, in relation to the ideas of D. Hume, which was the direct impetus for writing Critique of Pure Reason.
Kant, who published Critique of Pure Reason in 1781, is a philosopher of the late 18th century, but B. Russell, author of A History of Western Philosophy, begins his chapter on "Kant" by stating that "18th century philosophy was dominated by British empiricists." Kant's philosophy was established through deep ties with British empiricism.
J. Locke, the founder of British empiricism, advocated what Russell called "a revolutionary new theory at the time," that the source of knowledge is experience. However, this empirical philosophy did not go in the direction of guaranteeing the foundations of natural science, which had already flourished in the 17th century under Newton and others, but rather in the direction of casting doubt on its certainty.
Locke's epistemology was not realism in the sense of accepting the existence of the external world and matter as a matter of common sense, but rather a highly idealistic empiricism that followed in the footsteps of the continental rationalist philosophy of Descartes, Spinoza, and Leibniz, which held that the external world could be known through the mind.
The British empiricists who followed him were also children of rationalism, and worked hard to make Locke's epistemology, which remained an eclectic compromise between ideas and reality, more consistent. As a result, G. Berkeley drove empiricism to idealism, and Hume drove empiricism to skepticism.
Of the three traditional concepts in philosophy - God, mind, and matter - Berkeley denied the existence of matter, while Hume denied the existence of mind, describing the ego as a "bundle of perceptions".
By breaking down the mind into perceptions, Hume's epistemology further advanced Berkeley's empiricist position, which viewed the external world as ideas. He came to understand the causal relationship that was thought to exist between two events as the mere juxtaposition of two perceptions.
Based on the observation that the two perceptions corresponding to each event do not contain the idea of a "necessary connection," he concluded that the "cause-effect" relationship in which event A is always followed by event B is due to a psychological habit formed from the repeated experience of perceiving A followed by perceiving B.
Kant realized the importance of this Hume's denial of the law of causality and said that "interrupted my dogmatic slumber," and he begins his Critique of Pure Reason with the following statement:
" For whence could experience derive its certainty, if all the rules, according to which it proceeds, were always themselves empirical, and therefore contingent?" (B5）
At that time, one of the types of knowledge that was considered certain was what was understood to be "innate". Philosophers before Locke believed that reason has a innate (a priori) knowledge, and that solid knowledge can be obtained by recalling knowledge given to humans in advance by God or by recalling idea.
The other type of knowledge that was considered certain was logical. For example, it was understood that the certainty of the arithmetic that 2 + 2 = 4 is completely different from the certainty gained from repeatedly experiencing that combining two things with another two things makes four.
Namely, certain knowledge has been thought to be either logical or innate, but Hume correctly understood that the physical relationship of "cause and effect" in causation is different from the logical relationship of "reason and consequence" in mathematics.
Furthermore, since the empiricism on which Hume relies denies the innate possession of knowledge, these points, combined with those above, result in the denial of both logical certainty and a priori certainty in physical phenomena.
As a result, the law of causality was considered to be an empirical rule based on observation, that is, probabilistic knowledge, and it was concluded that seeing necessity or certainty in it was simply a misunderstanding of psychological habits acquired from repeating the same experiences.
In this situation, Kant takes up the question, "How is knowledge that is both empirical and certain possible?" and declares this question in the "INTRODUCTION".
"How are a priori synthetic judgments possible?"（B19）
Here, "a priori" means certainty, and "synthetic judgment" means empirical knowledge.
Not only in science but also in general everyday events, events are expressed not by logical statements that do not extend perception, but by extended (=synthetic) statements (=judgments) that include things not included in the initial perception.
For example, a logical statement that does not extend perception is the statement that concludes "man" from "tall man" in "A tall man is always a man." Also, a statement that extends perception is the statement that concludes "warm water" from "cold water" in "Putting cold water on the fire always warms it."
It is known that logical statements have certainty, but the question posed in the above "INTRODUCTION" is how "the necessity that it is impossible to reach any state of affairs other than a particular state of affairs" arises in empirical statements.
If this is not found, it follows that the certainty of all science cannot be guaranteed. However, Kant believes that such empirical and certain judgments already exist in reality, that is, the law of causality is a certain rule, and therefore there is no doubt that science exists with certainty. Nonetheless, the principle by which this is realized has not yet been found, so Kant thought it was my job to find it.
Kant attempts to discover this principle through his own unique method, the "Critique of Reason". Kant's idea for finding this was a view of cognition that reversed the traditional subjective-objective relationship.
"What will happen if, we assume that rather than perception following the object, the object follows perception?"（BXVI）
―― Until now, we have thought that external phenomena exist first, and that our perception captures them later. However, as long as one takes this view of cognition, laws such as causality must be obtained from experience, which would lead to Hume's skepticism. So what if we reverse this idea and suppose that we ourselves give rules to our experiences, or rather, that our experiences and perceptions would not exist without those rules? ――
Based on this idea, Kant believed that we are innately endowed to our subjective faculties with principles that give laws and principles that give rise to experience.
In other words, the principle of giving laws is due to the fact that the concept-forming ability of pure understanding is endowed with a logic consisting of 12 categories, including the law of causality, and the principle that gives rise to experience is due to the recognition of space and time in the innate subjective ability of pure intuition.
This deductive proof of pure understanding and pure intuition forms the first half of the Critique of Pure Reason.
It should be noted that the a priori knowledge presented here as the acquisition of certainty is not the certainty in the sense of the impartation of divine knowledge that was thought of before Kant. After such theological residues were removed, another type of certainty, that of logic, was introduced into innate nature in the form of the "Category", drawing on Aristotelian logic.
Therefore, the "transcendental logic" that concludes the first half of Critique of Pure Reason was created as a logic that is certain because of its logic and is also related to its object. This name contrasts with Aristotle's "formal logic", which is logical and therefore certain, but is not concerned with objects.
This is how Kant's theory of epistemology, known as "epistemological subjectivism," is established, which necessitates that all our experiences have causal behavior. This is because, in this view of cognition, rules that exist in our subjectivity are assigned to objects, and "objects follow cognition".
However, if we try to understand what it means that "objects follow cognition" without taking into account the Critique of Pure Reason's definitions of space and time, this idea will seem strange. For it is patently absurd to claim that the objects before us somehow interact with each other according to the rules of our understanding.
Nonetheless, the reason this seems strange is that it is stuck in a view of cognition that existed before the Critique of Pure Reason, which sees objects in the external world as entities independent of us.
According to Kant, the objects that are said to exist in the external world can only exist through the action of pure intuition, which recognizes space and time. There is no matter that does not extend or persist, that is, that does not require space and time. However, if space and time are created by pure intuition, which is our subjective ability, then the things we perceive as material can only exist by waiting for our subjectivity.
Therefore, the statement that "objects follow cognition" is not something that is asserted only about the lawful behavior of things. The experiential world including objects are themselves "phenomena" created by our cognition. This is the argument of Kant's "epistemological subjectivism".
The above is the content of the first half of the Critique of Pure Reason. This view of Kant gives rise to a dualistic world consisting of "phenomena" as the empirical world in which things occur according to scientific laws, and "thing in itself" as the transcendent world that is not bound by laws.
The experiential world that our subjectivity creates is a world that is spatial, temporal, and logical. Things that transcend space and time and things that deviate from logic and laws cannot exist in the empirical world.
However, this does not exclude such transcendent beings, but rather suggests that their existence is possible outside of our experience. "Transcendental Dialectics" in the latter half of Critique of Pure Reason is an argument that, by assuming the existence of such "thing in itself", solves all of the traditional problems that faced metaphysics at the time.
In this way, Kant demonstrated the validity of the idea of "thing in itself", and perhaps for the first time, gave rationality to the transcendent world, which had previously been assumed only through faith or popular belief, as a philosophical theory. This point is what I understand to be the most groundbreaking part of Kant's philosophy, along with the idea that reason itself criticizes its own abilities.
Kant's thought, which has this nature, was initially understood to be in line with the biblical view of God.
"No one has ever seen God"（1 John 4:12 NIV）
"God's invisible qualities"（Romans 1:20 NIV）
"The secret things belong to the Lord our God"（Deuteronomy 29:29）
Kant's new idealism was understood as something that protected faith from the threat of the sciences, and was welcomed by Christians up to the end of the 19th century, including liberal theologists such as E. Troeltsch and A. Ritschl.
However, the worldview presented by Kant had serious flaws from the perspective of the Christian worldview. It is what is called the "separation of phenomena and things in themselves", and Kant's dualistic world results in no communication between our experience and the Christian God.
Because God is a being that is neither spatial nor temporal, it is impossible for humans to know God, and there can be no revelation from God as a propositional statement either. In Kant's theory, God can exist and non-causal miracles can occur, but only outside of human experience.
This inability to know God was a direct harm to Christianity brought about by the Critique of Pure Reason, and those who tried to overcome this gave rise to a type of Christianity called liberal theology, which differs from traditional Christianity.
To them, belief in revelation and miracles was merely a naive belief that existed before the appearance of the Critique of Pure Reason, and more accurately, it was a mistaken belief.
This alone can be considered a major event in the history of Christianity, but the changes that Critique of Pure Reason demanded of Christianity were not limited to the inability to recognize God or experience miracles. This became clear in the late 19th century with the Gospel studies of W. Vrede and others, and they concluded that not only is it impossible to know the transcendent God, but also the immanent historical Jesus.