"Where is the boundary for the single individual in his concrete existence between what is lack of will and what is lack of ability; what is indolence and earthly selfishness and what is the limitation of finitude? For an existing person, when is the period of preparation over, when this question will not arise again in all its initial, troubled severity; when is the time in existence that is indeed a preparation? Let all the dialecticians convene-they will not be able to decide this for a particular individual in concreto."