It is always perfectly justifiable to distinguish between error as such and the person who falls into error—even in the case of men who err regarding the truth or are led astray as a result of their inadequate knowledge, in matters either of religion or of the highest ethical standards. A man who has fallen into error does not cease to be a man. He never forfeits his personal dignity; and that is something that must always be taken into account. Besides, there exists in man's very nature an undying capacity to break through the barriers of error and seek the road to truth. God, in His great providence, is ever present with His aid. Today, maybe, a man lacks faith and turns aside into error; tomorrow, perhaps, illumined by God's light, he may indeed embrace the truth. Catholics who, in order to achieve some external good, collaborate with unbelievers or with those who through error lack the fullness of faith in Christ, may possibly provide the occasion or even the incentive for their conversion to the truth.
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?