PROP. XVII.————
Its contradictory character exposed in so far as it is psychological.phenomenon (Prop. XVI. Dem., Prop. XIV. Dem.) The known substantial is whatever, and only whatever, can be known or thought of without anything else being known or thought of along with it. Does anything else require to be known or thought of along with objects plus a subject, or along with matter mecum, or along with the universal + the particular? It is obvious that nothing else does (see Props. II. III. VI.) Does anything more require to be apprehended than the ego or oneself in some determinate condition? Nothing more requires to be apprehended (Prop. IX.) Therefore this synthesis, however it may be expressed, is the substantial in cognition, and is established as such on necessary grounds of reason; and consequently the counter-proposition is the denial of a necessary truth of reason.
Again: The phenomenal is whatever, and only whatever, can be known or thought of only when something else is known or thought of along with it. Can object plus a subject—or can matter mecum—or can the universal + the particular—or can the ego or oneself in some determinate condition—can the synthesis of these be known only when something else is known along with it? No indeed. The synthesis can be known by itself, and unsupplemented by anything further. Therefore this synthesis is not the phenomenal in cognition, and is proved not to be this on necessary principles