For example, a smoker who wants to quit but can't resist the temptation of a smoke is an autonomous person but lacks strength of will (or character, or habitual rational moral acting). What would he say about how we treat that person? What would he say about:
- giving them obstacle to attain character (e.g. invite them to smoke)?
- creating obstacle for them to achieve the action (e.g. not letting them to smoke)?
And if for a moment they forget that they shouldn't smoke, and have a strong belief that what they need is a smoke, then would that new belief be their autonomy, or their lack of strength? Or would this question can only be answered after that, when they re-express their belief again?
This is the summary of the chapter Kant on Weakness of Will from the book Virtue, Rules, and Justice: Kantian Aspirations:
This chapter reviews the background in Kant’s moral psychology, suggests how weakness of will might be understood in Kant’s theory, and comments on the implications for moral responsibility. In brief, the proposal is this. For Kant, weakness of will is not a physical incapacity or disability but contrasts with virtue understood as developed strength of will to do our duty despite obstacles. The will is not literally a force, strong or weak, but is conceived as either law-giving practical reason (Wille) or choice to act on a maxim (Willkür). Morally weak persons choose to act on particular maxims in conflict with both practical reason and their general maxim to act as they should. Our general life-governing maxims, like laws of the state, may be weak in content (vague and indeterminate) or willed weakly (with little provision for implementation). Moral weakness mitigates culpability without excusing. Contrary to some interpretations, weak-willed bad acts are, in an important sense, freely chosen and not necessarily failed efforts to act well. How this is possible, in Kant’s view, cannot be explained empirically or metaphysically.
However, it doesn't say how should we treat weak-willed actors.