Does one say "I wonder what impelled him to do that" or "I wonder what induced him..."? Impel means "to drive or press on," "to incite," "to propel": "The angry speaker was impelled by his sense of injustice." "The coach's fiery talk to his players impelled them to play harder." Induce means "to lead or move by persuasion," "to bring about": "This medicine will induce sleep very quickly." "Your remarks have induced me to change my attitude." In the first sentence of this entry, use impelled if some force or outside influence was operating; use induced if some inner conviction led to action.
Dictionary of problem words and expressions. Harry Shaw. 1975.