Perhaps the ecumenical dizziness spun from the first Parliament of Religions (Chicago, 1893) and the horrific modern wars like the First World War (and their wearying effect on society) were on the mind of Pius XI when he wrote this encyclical (1928). Times were hard enough all over and people were tired: who wanted to fight about religion of all things? As a result, the cause of fostering unity among men of all religions—among those calling themselves Christians—was catching on fast and generating indifference, even among Catholics, to the objective truths of the True Faith. This ecumenism was being motivated by a false idea of “one flock” under the guise of a falsely-understood charity. Pius XI here denounces the dreamers, calls inconceivable a “federation of Christians in which each member retains his own opinions...in matters of faith,” and, proclaims that the only ecumenism is to convert the world to Catholicism.