Abū Bakr and ʿUmar after the Prophet—may Allah bless him and grant him peace—for had anyone else assumed authority, he would not have accomplished what they did, either because he lacked the capability or because he lacked the will.
Indeed, if it is asked:
“Why did ʿAlī not overcome Muʿāwiya and his supporters?”
The cause must have been either incomplete capability or incomplete will. Otherwise, when capability and will are complete, the act must necessarily occur. Complete capability includes having one’s followers obey him, while complete will includes willing (1) what is best, most beneficial, and most pleasing to Allah and His Messenger.
Abū Bakr and ʿUmar possessed fuller capability and a superior will. It was through this that Allah granted Islam victory by means of them and brought unbelief and hypocrisy low by means of them. ʿAlī—may Allah be pleased with him—was not granted the same fullness of capability and will that they were.
Just as Allah Most High favored some prophets over others, He favored some caliphs over others. Since ʿAlī was not granted what they had been granted, he could not accomplish during his caliphate what they accomplished. That being so, he would have been (2) far less capable still of doing so when the Prophet—may Allah bless him and grant him peace—died. No matter how the matter is construed, the most a Shiite can say is:
“His followers did not obey him.”
It is replied:
“If (3) those who pledged allegiance to him (4) did not obey him, how would those who had not pledged allegiance to him (5) have obeyed him?”
And if it is said:
“Had they pledged allegiance to him (6) after the death of the Prophet—may Allah bless him and grant him peace—he would have accomplished through them something greater than what Abū Bakr and ʿUmar accomplished.”