Kant's Philosophy and the Birth of Modern Science: Rationalism, Empiricism and Transcendental Idealism

Historical context: the Early Modern period

The period between the 15th and 18th centuries is known as the time of absolutism. Absolute monarchies organized administrative structures that, in many cases, undermined the power of the Church.

Two events were decisive for the birth of modern society:

• The Protestant Reformation, which favored modernity in Europe and broke the Catholic Church's monopoly in Western Europe. Protestantism promoted the reading of the Bible, which led to a process of literacy.
• The development of the printing press, which led to the organization of an educational system.

Modern society also began with Copernican astronomy. Copernicus replaced the geocentric view with a heliocentric one. His heliocentric model was incompatible with the absolute model of the time, and it fostered technological development.

Galileo began a new physics, and later Newton developed a new model of the universe. Modern science allowed a method through which abstract theories could be easily applied by technicians. With its help, the mastery of the universe triumphed, and this advance favored technical and scientific progress, which in turn led to capitalism.

Modern science combines deduction with induction. A consequence of the scientific method is to observe that there are measurable qualities. Because they are measurable, science seeks to mathematize results, giving them universality. All this universality must be expressed in numbers. The success of modern science in expressing universality caused concern about the limits of knowledge.

The two main parts of philosophy developed in parallel from this time: knowledge and political philosophy. Modern science showed an extraordinary efficiency, and this raised the question: how do we know?

Two philosophical currents: Rationalism and Empiricism

Two philosophical currents emerged: rationalism and empiricism.

Rationalism

Rationalism is the father of Descartes. Spinoza, Leibniz and others are important philosophers of this current. Rationalism holds that all our knowledge is deductively constructed from a series of innate principles (ideas that belong to the human being by nature). These are the first innate principles, whose truth is guaranteed by their clarity and distinction. Rationality, not empirical observation or the senses, is the only source of truth.

Rationalism uses deduction in logic and mathematics. Mathematics starts from axioms, which are true first principles. From these axioms, rationalism derives ideas. Because these principles are innate, their truth is guaranteed. This is why modern philosophy emphasizes the active role of the subject in the construction of knowledge.

We perceive through the senses, but the senses can be a source of deceit. Cogito, ergo sum (I think, therefore I am). Descartes distinguishes three types of substances:

• Thinking substance (the self or eu)
• Extended substance (matter, in terms of extension)
• Infinite substance (God)

A substance is that which needs nothing external in order to exist. Only a single substance fits this definition: the infinite substance, God. Descartes nonetheless recognizes the three kinds of substance. A later current of rationalist criticism questioned these metaphysical premises.

Empiricism

The founder of empiricism was the English philosopher Locke, and the most important is Hume. Empiricism holds that all our knowledge has its origin and limit in sensible perceptions. All human knowledge is acquired through experience. Empiricism recognizes that human knowledge has limits.

The principal difference is that rationalism holds that some ideas are innate, while empiricism holds that we acquire everything through experience. Our knowledge is acquired through impressions and ideas. Impressions are immediate perceptions that strike our mind with force. Ideas are the faint copies of impressions that remain in our mind when impressions disappear. Ideas derive from impressions.

Empiricism leads to skepticism, since we cannot be sure of the truth of knowledge, because knowledge is subjective. If we ask where the idea of substance thinking comes from, and where the idea of extended substance comes from, empiricism answers that they come from impressions, not from reason.

Thinking substance / the self

Descartes supposes that a substantial entity exists, self-sufficient, that endures over time, self-conscious, which we call the self. It is true that, from a sensible impression, one should be able to derive characteristics such as self-sufficiency, permanence and the like, from its own life. But in fact we only find a succession of impressions, feelings and moods, never a substantial entity. When sensible impressions disappear, the self disappears too. What exists is only a succession of sensible impressions that we call the self, and it is not anything substantial. This is a metaphysical principle.

A rationalist critique of the concept of extended substance holds that we cannot know its causes, because our impressions are limited. Since we cannot know either of them, we cannot know extended substance. It may exist, but we cannot prove it.

Kant and the Transcendental Idealism

Kant's Copernican Revolution

For Kant, the Enlightenment achieved its full realization in the use of reason with autonomy, without external guidance and without dogmatic limits. Freedom is only possible as the result of the autonomous exercise of reason. Since freedom implies responsibility, many people prefer to delegate responsibility to others. Daring to know is the motto of the Enlightenment.

The division of knowledge

There is a division in knowledge. Kant prefers this approach. Rationalism claims truths that cannot be proved in the early stages, while empiricism puts knowledge at the mercy of experience. Kant seeks a critique of reason. Kant's Critique of Pure Reason analyzes the use of pure reason, and his Critique of Practical Reason addresses questions of morality and ethics. The Foundations of the Metaphysics of Morals analyzes practical reason. The Critique of Pure Reason asks whether metaphysics is possible as a science, that is, whether it is possible to construct a metaphysics that has the validity and objectivity of scientific knowledge.

The Copernican revolution in philosophy

Kant's critical revolution is the Copernican revolution applied to metaphysics. Copernicus changed the perspective to solve problems. In the same way, Kant changed the perspective of metaphysics: the object of knowledge must adapt to the conditions of the subject, and not the other way round, as had been assumed until then. Knowledge is the result of experience and understanding. Understanding provides rules (elements) that are not found in experience. These a priori elements of understanding make experience possible. Knowledge consists of the subject, endowed with a priori structures, organizing the data of experience into the objects we comprehend.

Judgment

A judgment is a statement about reality. We express our knowledge of reality through judgments. Judgments can be analytical (where the predicate is contained in the subject) or synthetic (where the predicate adds something not contained in the subject). They can also be a priori (independent of experience, always analytical) or a posteriori (dependent on experience, synthetic or analytical). Synthetic a priori judgments extend our knowledge beyond experience while being universally valid. They are the basis of scientific knowledge. If they are possible, they explain how scientific knowledge is possible, and by the same token how metaphysical knowledge is possible.

Experience as the starting point

For Kant, all knowledge begins with experience. But not all knowledge arises from experience, because we also need understanding.

Faculties of knowledge

Which faculties intervene in the construction of knowledge? Two: sensibility and understanding. Knowing means affirming a connection between the two. Knowledge is only possible through the joint action of sensibility and understanding.

Transcendental conditions

Kant's Transcendental Doctrine of the Elements analyzes the transcendental conditions that make human knowledge possible. It is divided into two parts:

• Transcendental Aesthetic: analyzes the a priori elements of sensibility. Kant seeks to clarify how synthetic a priori judgments are possible in mathematics and physics.
• Transcendental Logic, which is divided into two parts: Transcendental Analytic, which analyzes the a priori elements of understanding, and Transcendental Dialectic, which analyzes why thought goes beyond experience and how synthetic a priori judgments in metaphysics are possible.

In addition to the Transcendental Doctrine, there is the Transcendental Methodology, which is the correct use of the elements of transcendental knowledge.

Transcendental Aesthetic: sensibility

Sensibility is the capacity to receive impressions. It captures everything in the form of intuitions (sensible impressions). Intuitions can be pure (without content, the form of intuition, the structures that make knowledge possible through the senses: space and time) or empirical (the content of intuition, the sensible qualities of objects). Sensible knowledge is our knowledge of the empirical intuitions perceived in a three-dimensional space and in a linear time. Pure intuitions are the transcendental conditions of sensible knowledge. Synthetic a priori judgments are possible because they are valid for space and time. Mathematics, specifically geometry, describes space and time, which are a priori conditions of our knowledge, and helps us to know them. Sensibility is a merely passive power, because it only receives intuitions.

Transcendental Analytic: understanding

Understanding thinks the intuitions provided by sensibility. Thinking means giving meaning to sensible intuitions. It is an active faculty, because it produces representations. Understanding uses concepts to think intuitions. Concepts can be pure or empirical. Empirical concepts are formed by abstraction from intuitions of sensibility. Pure concepts, or categories, are the forms of thought. Categories are innate: they are the a priori conditions of understanding, and therefore they lack empirical meaning on their own. For Kant, we can only know which categories exist and what their function is through judgments, because judgments are possible thanks to the categories (the transcendental deduction of the categories). There are 12 categories (for example, cause). Through these categories, we understand reality.

We know phenomena, that is, empirical reality, through the transcendental conditions of sensibility and understanding. Through the categories, space and time, we know things as they appear to us. Categories make synthetic a priori judgments possible. We know the phenomenon, but we do not know things as they are in themselves. Things in themselves exist independently of us and of our subjective determinations; they are called noumena. The noumenon is the thing that underlies the phenomenon, and it is connected to the subject only through the subject's transcendental conditions of knowledge. Objectivity, for Kant, is to be applied to the transcendental conditions of knowledge derived from intuitions.

Transcendental Dialectic: reason

Kant offers a possible answer to synthetic a priori judgments in metaphysics: that is, how metaphysics can be a science. Human reason seeks general knowledge, that is, knowledge that goes beyond the immediate. Reason is the fundamental faculty that generates judgments that go beyond experience, and seeks ever more general and unifying principles. When we try to use reason beyond experience, reason produces illusions. For Kant, only the reasonings that apply categories to intuitions are valid. Three objects of traditional metaphysics result from this illegitimate use of reason:

• Extended substance (the world): an attempt to explain the physical phenomena of the world through metaphysical theories.
• Thinking substance (the soul): an attempt to explain psychic phenomena of the self through metaphysical theories.
• Infinite substance (God): an attempt to explain physical and psychic phenomena through metaphysical theories about the world and the self.

The result of these leaps beyond the limit of what can be verified is that they cannot be known. Experience has no access to them, so they cannot be objects of scientific knowledge. Metaphysics cannot be a science, because its synthetic a priori judgments are based on an illegitimate use of the categories. Nevertheless, these three ideas have value for reason. They are the aspiration to know reality in its ultimate principles.

Practical reason: ethics and morality

Practical reason is concerned with what we ought to do. It tells us how we should behave socially. The most important problem for any ethics is whether it can be accepted by everyone in society. Kant proposes an ethics that is universal, independent of any particular situation. For Kant, there are two types of ethics:

1. Material ethics: when one pursues an end, such as happiness or the supreme good that humans aim to reach. These material ethical mandates are empirical (a posteriori), not universalizable, because they refer to concrete cases. Situational precepts are conditional, that is, subordinated to the attainment of a supreme end.
2. Formal ethics: the mandates derive from reason itself. Material ethics cannot be universalized. It must be a pure ethics, absolute and autonomous: a formal ethics. It is pure because it says how we should behave at all times without establishing concrete behaviors; it is absolute because it is independent of the situation; and it is autonomous because its principles derive from reason itself.

Duty and the categorical imperative

To achieve a formal ethics, Kant uses two basic concepts: duty and the categorical imperative. Duty is the necessity of performing an action out of respect for the law. Morality in action arises from duty, in Kant's own words. There are three types of actions:

• Actions against duty: immoral actions, performed intentionally.
• Actions in conformity with duty: actions that are morally correct but performed for reasons other than duty, such as self-interest.
• Actions from duty: actions done morally, out of duty, as an end in itself.

What is the categorical imperative? Duty is expressed through a mandate that derives from reason. Reason tells us what we ought to do. There must be an absolute rule that reason gives us, called the categorical imperative: it tells us how we must always act. Material ethical mandates are hypothetical, because their value depends on a concrete action. The categorical imperative is universal law.

What is the categorical imperative, exactly? I must always act only in such a way that I can also will that my maxim become a universal law.