raised by human experience, the latter uses _reason enlightened by Divine Revelation_ to study the contents of this Revelation in all their bearings on man’s life and destiny. Hence we arrive at this simple and widely accepted definition of philosophy: _the science of all things through their ultimate reasons and causes as discovered by the unaided light of human reason_.(5) The first part of this definition marks off philosophy from the special sciences, the second part marks it off from supernatural theology. We must remember, however, that these three departments of knowledge—scientific, philosophical, and revealed—are not isolated from one another in any man’s mind; they overlap in their subject-matter, and though differing in their respective standpoints they permeate one another through and through. The separation of the special sciences from philosophy, though adumbrated in the speculations of ancient times and made more definite in the middle ages, was completed only in modern times through the growth and progress of the special sciences themselves. The line of demarcation between philosophy and supernatural theology must be determined by the proper relations between Reason and Faith: and naturally these relations are a subject of debate between philosophers who believe in the existence of an authentic Divine Revelation and philosophers who do not. It is the duty of the philosopher as such to determine by the light of reason whether a Supreme Being exists and whether a Divine Revelation to man is possible. If he convinces himself of the existence of God he will have little difficulty in inferring the _possibility_ of a Divine Revelation. The _fact_ of a Divine Revelation is a matter not for philosophical but for historical research. Now when a man has convinced himself of the existence of God and the fact of a Divine Revelation—the _preambula fidei_ or prerequisite conditions of Faith, as they are called—he must see that it is eminently reasonable for him to believe in the contents of such Divine Revelation; he must see that the truths revealed by God cannot possibly trammel the freedom of his own reason in its philosophical inquiries into ultimate problems concerning man and the universe; he must see that these truths may possibly act as beacons which will keep him from going astray in his own investigations: knowing that truth cannot contradict truth he knows that if he reaches a conclusion really incompatible with any certainly revealed truth, such conclusion must be erroneous; and so he is obliged to reconsider the reasoning processes that led him to such a conclusion.(6) Thus, the position of the Christian philosopher, aided in this negative way by the truths of an authentic Divine Revelation, has a distinct advantage over that of