Briefly, dialectics for Plato represented the highest degree of knowledge, for Aristotle it was a probabilistic syllogism, whereas for Kant it is the analysis of the obstacles to reason. Kant adopts a negative connotation of dialectics and defines it as the Logic of Schein (Appereance). According to Kant, Reason has a structural tendency to move beyond the realm of experience into the unknowable, and in doing so, it commits a series of errors. For Kant, this is a characteristic proper to reason, ‘for senses do not err, not because they always judge correctly, but because they do not judge at all’ (p.208 CPR)

There can be empirical illusory appearances (such as optical ones), but here Kant is concerned with transcendental illusory appearances, arising when ’the subjective necessity of a certain connection of our conceptions, is regarded as an objective necessity of the determination of things themselves.’ (p. 210)

These illusions are impossible to avoid. Here Kant is very clear on the structural necessity and inevitability of these errors. How does this occur?

The Transcendental Analytics had set out to demonstrate the existence of a priori forms and pure concepts of the understanding that preceded experience. It also specified that these were nothing in themselves unless considered as conditions of experience (whether real or possible). Whenever Reason attempts to move beyond possible experience, it falls into error and illusion. Transcendental illusions are not causal, but natural. They are neither dependent on the will not avoidable. The transcendental dialectics is a critique of such illusions. It aims to show the limits and transgressions of reason in order to avoid unscientific conclusions and guard against metaphysical dogmatism.

 Unlike sophistic and heuristic dialectical illusions, transcendental illusions cannot be eliminated, even once they are exposed. It requires a continuous labour of critique to remove the momentary errors reason commits by its own very structural nature.

However, there is a logic to the error man commits when going beyond experience, and in fact, the last section of the critique is devoted to the examination of these errors and to ways to discipline the excesses of reason. Hence, dialectics for Kant includes both the study and critique of transcendental illusions.

To summarise again then: transcendental aesthetics studies the capacity for receiving representations (receptivity), i.e. sensibility, the tenet of sensible knowledge being intuition. Transcendental Analytics studies the understanding and its laws (spontaneity) with thought as the synthetic activity of elements of pure cognition. Transcendental dialectics studies Reason and its structures.

But what is Reason for Kant? Kant recognises reason in its generic connotation as the knowing faculty; however, he also provides it with a specific meaning in the dialectic, which will become very popular during the Romantic period to come.