“Catholic theology recognizes that natural revelation is the preparation for and the presupposition of, supernatural revelation; and also that he who has to some extent assimilated the theistic and spiritual teaching of nature is best able to understand and appreciate the truths of supernatural revelation.
“We need both forms of revelation. The natural prepares us for the supernatural, and cannot be violated or stultified by it, but remains true forever. On the other hand, natural revelation is partial and unsatisfying apart from supernatural revelation, and affords insufficient guidance in the fulfilment by men of the divine purpose for which they were made. Moreover, it is only in the light of supernatural revelation, whether this light be properly ours or unwittingly borrowed from others, that we are able to acquire anything approaching an adequate understanding of what nature teaches. Yet the teaching of nature is amply sufficient to convince genuine truth-seekers that God exists, and that He is their supreme Guide, and sovereign Object of adoring service; and it puts men to a real probation of faith and obedience.
“Supernatural revelation accomplishes two things in relation to nature’s teaching: republishing it in clearer and more definite terms; and supplementing it by truths which could not otherwise be known by us, but which we need to know in order to come into right personal relations with God and advance intelligently to our divinely appointed destiny.”
The Being and Attributes of God, Francis J. Hall, D.D., New York:Longmans, 1918, pp. 225-226.
It seems to me that without both natural and supernatural revelation, we might be divided within ourselves, between what we believe based on our senses and our reason, and that which we believe based on feelings and sentiments of truth, beauty and goodness. Having both enables us to unify our grounds of belief from what would otherwise be two separate spheres, so that we may give a unified and wholehearted assent.