If a person requires proofs of God's having been manifested to us in the flesh, let him look at the Divine activities. For of the existence of the Deity at all one can discover no other demonstration than that which the testimony of those activities supplies. When, that is, we take a wide survey of the universe, and consider the dispensations throughout the world, and the Divine benevolences that operate in our life, we grasp the conception of a power overlying all, that is creative of all things that come into being, and is conservative of them as they exist.
On the same principle, as regards the manifestation of God in the flesh, we have established a satisfactory proof of that apparition of Deity, in those wonders of His operations; for in all his work as actually recorded we recognize the characteristics of the Divine nature. It belongs to God to give life to men, to uphold by His providence all things that exist. It belongs to God to bestow meat and drink on those who in the flesh have received from Him the boon of life, to benefit the needy, to bring back to itself, by means of renewed health, the nature that has been perverted by sickness.
It belongs to God to rule with equal sway the whole of creation; earth, sea, air, and the realms above the air. It is His to have a power that is sufficient for all things, and above all to be stronger than death and corruption. Now if in any one of these or the like particulars the record of Him had been wanting, they who are external to the faith had reasonably taken exception to the gospel revelation. But if every notion that is conceivable of God is to be traced in what is recorded of Him, what is there to hinder our faith?
Source: The Great Catechism (New Advent)