Case: Someone has the health and means to perform a required act but does not do it. Does non-performance prove that no ability existed beforehand?
Prior capacity—health, means and opportunity—relates to the conditions of obligation. The enabling grace accompanying an act concerns its actual occurrence. The two senses of capacity are not interchangeable.
A person who has sufficient means cannot automatically evade an established duty by saying that the act did not happen. The obligation and the ability relevant to it still need to be considered.