15 It was at such a time and under pressure of such circumstances as these that Leo XIII wrote his social encyclical, Rerum Novarum , based on the needs of human nature itself and animated by the principles and spirit of the Gospel. His message, not unnaturally, aroused opposition in some quarters, but was received by the majority of people with the greatest admiration and enthusiasm.
Source: Mater et Magistra (Vatican.va)