Kant's Transcendental Philosophy: A Priori Forms and Practical Reason

1. Space and Time: The A Priori Forms of Sensible Intuition

Space and time are a priori forms, formal elements that affect the subject, as space and time are pure intuitions. Every sensation is multifaceted and occurs in space and time. Space is not an empirical concept; it is the condition of the possibility of phenomena. Besides, finite magnitude in space is to geometry as time is to arithmetic. We understand geometry as synthetic knowledge a priori. Therefore, space is not a property of things in themselves but the way the phenomena of the external senses appear to us.

Time is the basis for all intuitions, so different times are not simultaneous but successive. It is a pure form of sensible intuition and is a unique time. Therefore, these a priori elements form the basis of the general theory of movement. Just as all phenomena of outer sense are in space, time is the form of the internal sense. However, as the external reduces to the internal, then all space is temporary, as Descartes suggested. Similarly, arithmetic is based on time, and space is reducible to time; thus, geometry is reducible to arithmetic. Time does not exist by itself but is the form of inner sense and the formal condition a priori of all phenomena. The pure intuitions enable the existence of synthetic judgments a priori in mathematics.

2. The Categories of Understanding

The categories are not understood as space and time (which belong to sensitivity). The forms of understanding concepts must be pure, should not belong to intuition, and must be systematic. Thus, the pure concepts of understanding are the categories.

Kant's Table of Categories includes 12 categories or forms of judgment, organized into 4 sections.

The categories are useful for thinking about objects and unifying areas of experience. The categories function as forms of judgment. The synthetic unity provided by the categories can only be applied to experience; they cannot be applied beyond possible experience and must apply to intuitions. The categories have no application when separated from sensibility. When applied to empirical concepts without corresponding empirical intuitions, they are empty. The categories have no empirical meaning, meaning we cannot apply them to concepts like God. They are deduced from the types of judgments.

5. The Postulates of Practical Reason

The postulates of practical reason include one negative and three positive elements. The negative result stems from the Critique of Pure Reason, which established that metaphysics is not a science because synthetic judgments a priori cannot be made regarding transcendent objects, as the categories do not apply to God but only to phenomena and pure intuitions.

The positive function prevents speculation in metaphysics and allows us to establish the necessary conditions for Practical Reason. God, the immortal soul, and freedom are necessary assumptions for moral action. The postulates of practical reason serve as the bridge between theory and practice. The postulates are statements that cannot be proved but are accepted as a basis for morality:

• Freedom

  It is assumed that we are free. We must admit that man is free to discuss moral action, because we cannot morally blame anyone for their actions unless we assume that the man who acted was a free man.

• Immortality of the Soul

  The goal of moral action is perfection, which cannot be achieved in a finite life. Therefore, only the immortal soul can attain this perfection.

• God's Existence

  God's existence is postulated because God provides the synthesis of perfection and happiness (the highest good), a synthesis that occurs only through God.