The “Investiture Controversy” centered primarily on the question of who had the right to appoint a bishop. The term “investiture” refers to “putting on the robes of office,” raising the question of who is entitled to make such appointments. Especially during the tenth century, this had been seen as the prerogative of a local ruler or patron. By appointing a local bishop or abbot, a patron could expect to exercise influence over their decisions, and possibly benefit financially from them. Gregory confirmed what other eleventh-century popes had already declared – namely, that the right to make such appointments lay with the pope, not with the secular authorities. In 1074, Gregory declared: “Those who have been advanced to any grade of holy orders, or to any office, through simony, that is the payment of money, shall hereafter have no right to officiate in the holy church.”
The emperor Henry IV reacted strongly against these proposals, rejecting the pope’s right to make such appointments. As if to emphasize his disagreement with the pope, he appointed his personal chaplain as bishop of the Italian city of Milan, knowing that Gregory had already determined that another Milanese priest should have the job. Relations between pope and emperor became so poor that Henry declared his own nominee to be pope, and tried to depose Gregory.