Aeterni Patris §8

⁸ But in order that philosophy may be bound equal to the gathering of those precious fruits which we have indicated, it behooves it above all things never to turn aside from that path which the Fathers have entered upon from a venerable antiquity, and which the Vatican Council solemnly and authoritatively approved. As it is evident that very many truths of the supernatural order which are far beyond the reach of the keenest intellect must be accepted, human reason, conscious of its own infirmity, dare not affect to itself too great powers, nor deny those truths, nor measure them by its own standard, nor interpret them at will; but receive them, rather, with a full and humble faith, and esteem it the highest honor to be allowed to wait upon heavenly doctrines like a handmaid and attendant, and by God's goodness attain to them in any way whatsoever. But in the case of such doctrines as the human intelligence may perceive, it is equally just that philosophy should make use of its own method, principles, and arguments-not, indeed, in such fashion as to seem rashly to withdraw from the divine authority. But, since it is established that those things which become known by revelation have the force of certain truth, and that those things which war against faith war equally against right reason, the Catholic philosopher will know that he violates at once faith and the laws of reason if he accepts any conclusion which he understands to be opposed to revealed doctrine.