Character and Constancy

Schopenhauer's defense of his thesis that 'Character is constant' is that any apparent evidence to the contrary, e. g. a deviation from a previously posited behavior pattern, is only a counter-example to a provisional empirical generalization, and, hence, is perhaps an occasion for the formulation of an improved empirical generalization, not for the jettisoning of the thesis.  However, that defense exposes its own weakness.  For, by arguing that the thesis is unfalsifiable by empirical evidence, it exposes it as a purely speculative proposition, in which case it is just as unverifiable by such evidence as well.  Instead, as any Kantian should know, the appropriate defense of a speculative proposition treats it as a heuristic hypothesis, the criterion of the value of which is its fruitfulness, or more precisely, its fruitfulness in comparison with competing heuristic hypotheses.  Hence, its not even entertaining alternative possibilities, e. g. that the 'Will-to-Evolve' is the intelligible character of a human being; that rigidity of Character bespeaks stagnation; that interpreting a deviation from a  perceived behavior can be a stimulant to analytical innovation; etc. exposes his presented argument as inappropriate for its own ambition.