PROPOSITION XVI.
THE SUBSTANTIAL IN COGNITION.
DEMONSTRATION.
The first premiss fixes the definition of known substance: "Whatever can be known without anything else being, of necessity, known along with it, is a known substance." But some such thing must be known, otherwise all knowledge would be impossible; because it is obvious that no knowledge could ever take place, if, in order to know a thing, we always required to know something else, and if, in order to know the thing and the something else, we again required to know something else, and so on in infinitum. Under such an interminable process knowledge could never arise. But knowledge does arise. Therefore a point must be reached at which something is known without anything else being, of
