Our metaphysical exploration - an attempt to rectify the foundation of Kant's "transcendental philosophy" - led us to the findings that 1) number, which belongsto the category of allness, signifies the unity of the categories, 2) number is nothing but the product of the transcendental synthesis of the imagination in conjunction with the synthesis of apprehension and the synthesis of representations - synthesis speciosa and synthesis intellectualis - 3) the transcendental synthesis of the imagination, which stands under synthesis speciosa and synthesis intellectualis could operate in virtue of the regressive synthesis itself, yielding possibility itself of the category of community - number "1" or prime number or one and itself. Therefore, number, i.e., pure schema of magnitude is subject to the law of everything alterable in its spacetime-determination that everything that happens must find its cause in the appearances (of the previous state), which is space-time itself.