call upon(redirected from call upon them)
1. To order or require someone to do something: I call upon you to tell the truth.
2. To make a demand or a series of demands on something: Social institutions are often called upon to assist the poor.
3. To visit someone: I called upon an old friend when I was in New York.
4. To make use of some resource; draw on something: I knew the task would call upon my every resource.