The term 'call upon' can be used to describe a variety of actions. To PETITION is to make a formal request, while to NECESSITATE is to make something necessary. To CRAVE is to have an intense desire for something, and to ASK is to put forward a request. To SEE is to observe or look at something, and to TAP is to lightly hit or strike. To CITE is to quote or refer to a source, and to VISIT is to go to a place. To DEMAND is to ASK for something in a forceful way, and to ENJOIN is to order or instruct someone to do something. To INVOKE is to call upon a higher power, and to BESEECH is to plead or beg for something. To CONJURE is to summon a spirit or force, and to IMPRESS is to make a strong impression on someone. All of these words can be used to describe the action of calling upon someone or something.