The proof for the existence of God from degrees of perfection, sometimes called the Henological Argument, finds its best-known expression as the fourth of Thomas Aquinas's "Five Ways" in his Summa Theologiae Ia, 2, 3. It is here quoted in full:

The fourth way is based on the gradation observed in things. Some things are found to be more good, more true, more noble, and so on, and other things less. But comparative terms describe varying degrees of approximation to a superlative; for example, things are hotter and hotter the nearer they approach what is hottest. Something therefore is the truest and best and most noble of things, and hence the most fully in being; for Aristotle says that the truest things are the things most fully in being. Now when many things possess...