On the regulative use of the ideas of pure reason.

The outcome of all dialectical attempts of pure reason not only confirms what we have already proved in the Transcendental Analytic, namely that all the inferences that would carry us out beyond the field of possible experience are deceptive and groundless, but it also simultaneously teaches us this particular lesson: that human reason has a natural propensity to overstep all these boundaries, and that transcendental ideas are just as natural to it as the categories are to the understanding, although with this difference, that just as the categories lead to truth, i.e., to the agreement of our concepts with their objects, the ideas effect a mere, but irresistible, illusion, deception by which one can hardly resist even through the most acute criticism.

Everything grounded in the nature of our powers must be purposive and consistent with their correct use, if only we can guard against a certain misunderstanding and find out their proper direction. Thus the transcendental ideas too will presumably have a good and consequently immanent use, even though, if their significance is misunderstood and they are taken for concepts of real things, they can be transcendent in their application and for that very reason deceptive.