Abstract Kant, aware of the difficulty of the epistemological rational of religion which brings about religious experience, followed a new path in philosophy and, instead of beginning from the method of obtaining certain knowledge, started from the possibility of certain knowledge. He was deterred by research in the method of certain knowledge, which was the destination of rational religion, and therefore went beyond the epistemological limits. Instead, he went on a search for a foundation regarding epistemology and achieved this feat via a transcendental method. The transcendental method, which in general considers as its axis investigating the possibility of a priori certain epistemology, though it resolved the lacks of epistemology, had its own weaknesses which brought about the protest of Kant followers who, though loyal, breached their promise and though close, put distance between themselves and Kant. Fichte transformed the transcendental method by dialectic, and Schopenhauer, by returning to Barkley, ruined Kant’s transcendental method. The present paper reviews Schopenhauer’s passage through Kant’s method and shows that Schopenhauer, though he accepts Kant’s transcendental conditions, he opposes Kant’s transcendental reasoning, which Kant claims to have derived from purely transcendental sources. He also challenges the self-proclaimed object and the exemplification object and, eventually, chooses Barkley’s direct method in experimental idealism.