"Natural Religion" Misnomer

The Creation of Eve: Michelangelo, Sistine Chapel

If by natural religion we mean a religion based upon reason alone without any divine intervention in time and place, such religion does not exist, because there are no religious people who have ever claimed that they have not been affected in any way by God.

There was never a time or a place in which humanity was never the recipient of intercourse with God, e.g. Adam and Eve, the protogenitors themselves interacted directly with the Creator, and that interaction, for starters, is indelibly marked on the human experience.

The conscience of every man is an internal witness in the form of the divine tribunal of which morality is the social manifestation.

God's self-denial is a fundamental, simple and exclusive element of True Religion.

"The philosopher aspires towards a divine principle; the Christian, towards a Divine Agent."

Cf. Newman Sermon excerpt below, and his Sermon 2: The Influence of Natural and Revealed Religion Respectively. 

What we normally mean by the term "natural religion" is the "heathen" world, i.e. that portion of humanity whose particular revelation from God has not be authenticated (Jesus Christ, God made man, is the sure measure!)

...Now, in investigating the connexion between Natural and Revealed Religion, it is necessary to explain in what sense religious doctrines of any kind can with propriety be called natural. For from the abuse of the term "Natural Religion," many persons will not allow the use of it at all.

5. When, then, religion of some sort is said to be natural, it is not here meant that any religious system has been actually traced out by unaided Reason. We know of no such system, because we know of no time or country in which human Reason was unaided. {18} Scripture informs us that revelations were granted to the first fathers of our race, concerning the nature of God and man's duty to Him; and scarcely a people can be named, among whom there are not traditions, not only of the existence of powers exterior to this visible world, but also of their actual interference with the course of nature, followed up by religious communications to mankind from them. The Creator has never left Himself without such witness as might anticipate the conclusions of Reason, and support a wavering conscience and perplexed faith. No people (to speak in general terms) has been denied a revelation from God, though but a portion of the world has enjoyed an authenticated revelation.

6. Admitting this fully, let us speak of the fact; of the actual state of religious belief of pious men in the heathen world, as attested by their writings still extant; and let us call this attainable creed Natural Religion...