Bd Pope Pius IX, Bull Ineffabiblis Deus, Dec. 8, 1854

For the Church of Christ, watchful guardian that she is, and defender of the dogmas deposited with her, never changes anything, never diminishes anything, never adds anything to them; but with all diligence she treats the ancient documents faithfully and wisely; if they really are of ancient origin and if the faith of the Fathers has transmitted them, she strives to investigate and explain them in such a way that the ancient dogmas of heavenly doctrine will be made evident and clear, but will retain their full, integral, and proper nature, and will grown only within their own genus -- that is, within the same dogma, in the same sense and the same meaning (St Vincent of Lerins).