Immanuel Kant said this quote

“ Metaphysics, a completely isolated and speculative branch of rational knowledge which is raised above all teachings of experience and rests on concepts only (not, like mathematics, on their application to intuition), in which reason therefore is meant to be its own pupil, has hitherto not had the good fortune to enter upon the secure path of a science, although it is older than all other sciences, and would survive even if all the rest were swallowed up in the abyss of an all-destroying barbarism. Reason in metaphysics, even if it tries, as it professes, only to gain *a priori* insight into those laws which are confirmed by our most common experience, is constantly being brought to a standstill, and we are obliged again and again to retrace our steps, as they do not lead us where we want to go. As to unanimity among its participants, there is so little of it in metaphysics that it has rather become an arena that would seem especially suited for those who wish to exercise themselves in mock fights, where no combatant has as yet succeeded in gaining even an inch of ground that he could call his permanent possession. There cannot be any doubt, therefore, that the method of metaphysics has hitherto consisted in a mere random groping, and, what is worst of all, in groping among mere concepts.What, then, is the reason that this secure scientific course has not yet been found? Is this, perhaps, impossible? Why, in that case, should nature have afflicted our reason with the restless aspiration to look for it, and have made it one of its most important concerns? What is more, how little should we be justified in trusting our reason, with regard to one of the most important objects of which we desire knowledge, it not only abandons us, but lures us on by delusions, and in the end betrays us! Or, if hitherto we have only failed to meet with the right path, what indications are there to make us hope that, should we renew our search, we shall be more successful than others before us?―from_Critique of Pure Reason_. Preface to the Second Edition. Translated, edited, and with an Introduction by Marcus Weigelt, based on the translation by Max Müller, p. 17 ”