An objection notes that religious obligation often applies before performance. If capacity exists only during the act, would the person already addressed by the command be incapable? For instance, the obligation to pray arises when its time begins, before a person starts praying.
The answer is that valid obligation takes account of the soundness of the relevant faculties, means, and instruments, not the particular power accompanying an act that has not yet occurred.
Being addressed by a command, having the ordinary means to respond to it, and actually performing the specific deed are distinct stages. Their occurring at different times does not by itself imply an obligation imposed on someone who is incapable.