وهي حقيقة القدرة التي يكون بها الفعل
It is the reality of the power in association with which the act occurs.
Power related to the actual deed is not identical with general good health. It is capacity considered in its specific connection with the deed's occurrence. In the theological account being presented, God creates the power in the servant, and the servant acquires the deed through intention and choice.
A healthy hand is one condition for lifting a pen. Actually lifting it by choice at a particular moment is another matter. The claim that power accompanies the act concerns the latter relationship, not every everyday use of the word “able.”