36 But the enemies of the Church, though forced to acknowledge the wisdom of her doctrine, accuse her of having failed to act in conformity with her principles, and from this conclude to the necessity of seeking other solutions. The utter falseness and injustice of this accusation is shown by the whole history of Christianity. To refer only to a single typical trait, it was Christianity that first affirmed the real and universal brotherhood of all men of whatever race and condition. This doctrine she proclaimed by a method, and with an amplitude andconviction, unknown to preceding centuries; and with it she potently contributed to the abolition of slavery. Not bloody revolution, but the inner force of her teaching made the proud Roman matron see in her slave a sister in Christ. It is Christianity that adores the Son of God, made Man for love of man, and become not only the "Son of a Carpenter" but Himself a "Carpenter." It was Christianity that raised manual labor to its true dignity, whereas it had hitherto been so despised that even the moderate Cicero did not hesitate to sum up the general opinion of his time in words of which any modern sociologist would be ashamed: "All artisans are engaged in sordid trades, for there can be nothing ennobling about a workshop."
Source: Divini Redemptoris (Vatican.va)