The introduction of Humani Generis summarizes the Church's belief in the power of reason to recognize that there is a God and to distinguish between the basic principles of good and evil (natural law):
- 1. Disagreement and error among men on moral and religious matters have always been a cause of profound sorrow to all good men, but above all to the true and loyal sons of the Church, especially today, when we see the principles of Christian culture being attacked on all sides.
- 2. It is not surprising that such discord and error should always have existed outside the fold of Christ. For though, absolutely speaking, human reason by its own natural force and light can arrive at a true and certain knowledge of the one personal God, Who by His providence watches over and governs the world, and also of the natural law, which the Creator has written in our hearts, still there are not a few obstacles to prevent reason from making efficient and fruitful use of its natural ability. The truths that have to do with God and the relations between God and men, completely surpass the sensible order and demand self-surrender and self-abnegation in order to be put into practice and to influence practical life. Now the human intellect, in gaining the knowledge of such truths is hampered both by the activity of the senses and the imagination, and by evil passions arising from original sin. Hence men easily persuade themselves in such matters that what they do not wish to believe is false or at least doubtful.
- 3. It is for this reason that divine revelation must be considered morally necessary so that those religious and moral truths which are not of their nature beyond the reach of reason in the present condition of the human race, may be known by all mean readily with a firm certainty and with freedom from all error.
Science is methodologically atheist
Let's assume there is no God. Then everything has to happen by accident. The Big Bang just happens without any cause. All of life, including the brain, comes from random mutation and natural selection. If we can "explain" the universe and the development of life without reference to God, then we defeat those arguments that are based on the development of life, and if we defeat those arguments, then may we conclude that there is no God? Diff to say, "Not a valid argument for God" and to say, "We know that there is no God."
"We do not have to assume that there is a God in order to explain the development of life in the universe." But that does not imply that there is no God. The biologists assume the existence of a universe within which random mutations can be preserved by natural selection. No universe, no random mutations, no natural selection.
It's just like a little baby playing hide and go seek. It thinks that when its eyes are covered, you're not there. The scientists cover their eyes--close their minds--and think that they have proved that God is not there.
God is not a sensible being. Saying, "I do not see, hear, taste, touch, or smell God anywhere in the universe" is an idiotic statement. God is pure spirit. We cannot know a pure spirit by observing a bodiless being with senses designed to give us information about embodied realities. God can act without us being able to observe Him acting because He is not a thing among things. He is spirit at work in the world (Rahner: "Geist im Welt").
- Conc. Vatic. D.B., 1876, Cont. De Fide cath., cap. 2, De revelatione.