Usul al-Kafi
Book 3: The Book of Excellence of Knowledge

Chapter 31
The limit of person’s capability

281. 1. A believer asked Imam Ali ar-Reza (p) regarding the ability (individual capacity) of a person.
Translator’s note: Most probably, the believer wanted to comprehend the meaning of the Divine words occurring in verse 286 of the second chapter of the Noble Quran which are as follows: God does not impose on any soul but within its individual ability.
Imam Ali ar-Reza (p): A person can be called ‘fully able or capable’ if he satisfies four conditions. He must be free to perform the action (there must not be irremovable hurdles between him and the performance of the action), he must be fit (bodily or physically) to perform the intended action; his limbs must be functioning normally and he must possess the means bestowed on him by God for performing the intended action …

282. 2. A person asked Imam Jafar as-Sadiq (p) about the limits of the capacity of actions of men.
Imam Jafar as-Sadiq (p): Do you have the power to do something which cannot be done?
The Person replied in the negative.
The Imam (p): Do you have the power to abstain (yourself) from what has already been done?
Again the Person replied in the negative.
The Imam (p): At what time do you have the capacity (of doing and not doing)?
The Person confessed: I do not know.
The Imam (p): Verily God has created mankind and bestowed upon them some ability but has not entrusted all powers to them. So they have been given the power to do anything at the time of doing it ‘if they want’…

283. 3. A believer asked Imam Jafar as-Sadiq (p): Do the subjects of God have absolute freedom to do anything?
Imam Jafar as-Sadiq (p): When men want to perform any act, they can accomplish it through the power and ability bestowed on them by God.
The Believer, who was in need of further clarifications, asked: What exactly is this ability or capacity?
The Imam (p): The adulterer who has committed adultery was in possession of the means (endowed by God) to do so. But if he had abstained from adultery and not indulged in it, he would have had the ability and the power to do so. This power or ability of that person was neither less nor more before his performance of the act of adultery. But it was well within his choice to do that act or to abstain from it while he was indulging in it or abstaining from it.
The Believer: Then on what basis will that person be punished by God?
The Imam (p): On the basis of sound reasoning (irrefutable logic) and on the basis of the means or capability with which the person was provided. Verily, God never compelled any of His bondmen to commit a sin; neither did He destine paganism for anyone by His irrevocable intention. But when a person chooses (on the basis of his free will) to be a pagan then God determines the same fate for him and it is in the knowledge and intention of God that such people would measure.
Now the inquisitive believer asked the Imam (p): Has God intended them to be unbelievers?
The Imam (p): I do not say that. What I say is that God knew that they would never become believers so God also intended for them the same fate based on His knowledge about them and so this Divine Intention is by no means irrevocable but optional. His intention is on the basis of their choice.