Abstract: Transcendental dialectic is not the art of producing dogmatically illusion, but a critique of understanding and reason in regard to their «hyperphysical use». Transcendental dialectic is the endeavour of exposing the illusion involved in attempting to use the categories and principles of the understanding beyond the bounds of phenomena and possible experience. «All our knowledge begins with sense, proceeds thence to understanding, and ends with reason». Reason is both a logical and a transcendental faculty. As a logical faculty, it produces so-called mediated conclusions through abstractions, as a transcendental faculty, it creates conceptions and contains a priori cognitions whose object cannot be given empirically. Our reason has a structural and natural tendency to move beyond the realm of experience into the unknowable. 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.