Exertion, Freedom, Certainty.

Even if one fails in an attempt to do X, one has not failed in an attempt to attempt X. Indeed, the concept of an attempt to attempt is tautological, if not redundant. Hence, Exertion is independent of any of its objects, and incorporates a 'freedom' that is distinct from any that might be involved in choosing a specific course of action. Thus, broadening the Cartesian project to include Praxis can lead to the discovery that Exertion is in itself always Certain.