The argument from degrees, also known as the degrees of perfection argument or the henological argument is an argument for the existence of God first proposed by mediaeval Roman Catholic theologian Thomas Aquinas as one of the five ways to philosophically argue in favour of God's existence in his Summa Theologica. It is based on ontological and theological notions of perfection. Contemporary Thomist scholars are often in disagreement on the metaphysical justification for this proof.. According to Edward Feser, the metaphysics involved in the argument has more to do with Aristotle than Plato; hence, while the argument presupposes realism about universals and abstract objects, it would be more accurate to say Aquinas is thinking of Aristotelian realism and not Platonic realism per se.
The fourth proof arises from the degrees that are found in things. For there is found a greater and a less degree of goodness, truth, nobility, and the like. But more or less are terms spoken of various things as they approach in diverse ways toward something that is the greatest, just as in the case of hotter (more hot) that approaches nearer the greatest heat. There exists therefore something that is the truest, best, and most noble, and in consequence, the greatest being. For what are the greatest truths are the greatest beings, as is said in the Metaphysics Bk. II. 2. What moreover is the greatest in its way, in another way is the cause of all things of its own kind (or genus); thus fire, which is the greatest heat, is the cause of all heat, as is said in the same book (cf. Plato and Aristotle). Therefore there exists something that is the cause of the existence of all things and of the goodness and of every perfection whatsoever—and this we call God.