159 Again it is perfectly legitimate to make a clear distinction between a false philosophy of the nature, origin and purpose of men and the world, and economic, social, cultural, and political undertakings, even when such undertakings draw their origin and inspiration from that philosophy. True, the philosophic formula does not change once it has been set down in precise terms, but the undertakings clearly cannot avoid being influenced to a certain extent by the changing conditions in which they have to operate. Besides, who can deny the possible existence of good and commendable elements in these undertakings, elements which do indeed conform to the dictates of right reason, and are an expression of man's lawful aspirations?
Source: Pacem in Terris (Vatican.va)