The critical doctrine, divided into two courses, is presented as a reflection on the ability of the human intellect to know the truth in a scientific manner. Ideally, it studies three parts: 1. Critique: the “critical problem,” that is, the ability of the human intellect to reach the truth (an sit veritas). 2. Noetic: the nature of human truth attainable through the acts of the intellect (quid sit veritas). 3. Epistemological: the possibility (an sit) and nature (quid sit) of “scientific” knowledge, which sees the human intellect projecting itself organically onto the entire analogous horizon of being, in five original ways: as it is in itself (metaphysical sciences), as it is known by the mind (logical sciences), as it is loved by the will (ethical sciences); as it is found in bodies insofar as they are sensibly experiencable (physical sciences), or intelligibly quantitative (mathematical sciences).