But why is it impossible to doubt of the existence of thought? Because, replies Descartes, to doubt is to think. Hence in doubting itself we think; let us doubt as we will we never escape thinking.
But in affirming the fact of our thought, or thinking, and in being necessitated to affirm it, we affirm and are necessitated to affirm the fact of Self-Existence. This fact is, according to Descartes, above proof, as it is above doubt: our consciousness of it is the first or fundamental, as it is an absolute and indestructible, certainty. The place which this consciousness occupies in Cartesianism, as its cardinal point, demands for it special attention; while the diversity of opinions concerning the nature of the Cartesian expression in which the knowledge is embodied necessitates a special statement on the subject.
To simplify the question, we must consider that there are, as there can only be, two opinions regarding the nature of the famous Cartesian principle.
Descartes, in the expression "Cogito, Ergo Sum," must either be held to deduce the knowledge of self-existence from a higher (more general) knowledge, as, e.g., What thinks, is, phænomenon implies a substance, or simply to affirm the fact, that is, to announce it as a knowledge immediately evident. If the former alternative be true, it is manifest that this knowledge is no longer primary, is no longer fundamental, since there is a knowledge (viz., that from which it is inferred) which is re-
