Every corporeal creature is from God, For wherever unity is found in diversity, it must be referred to a single cause, because variety does not, by itself, unite things in one order. Since Being, therefore, is common to all things, however diverse, there must of necessity be some Principle of Being by which all things exist, whatever they are and according to whatever mode; and this Principle is God.
Corporeal creatures are created by God to manifest His Goodness, not by way of punishment; for every nature is good. Neither is the disposition of the universe accidental, but creatures all form parts of a whole, in which the parts exist for the sake of their utility and are ordered to the whole. The less noble are for the nobler, matter for form, single creatures for the universe, and the universe for God; since it forms a representation of the Divine Goodness, by means of which rational creatures may, in a special manner find their end in the love and knowledge of God.
The higher any cause is, the more it extends to variety in causation; but that which underlies things is always found to be more general than that which informs and individualizes them. Thus, Being is more general than life, and life than intelligence; and the more general anything is found to be, the more directly it proceeds from the First Cause; for no second cause can produce anything unless something be presupposed to the thing produced, either created or uncreated.
It remains, therefore, as before said, that God alone can create, and that corporeal forms are not produced from ideas (as taught by Plato and Origen); or created by lower intelligences (as held by Avicenna) - but that in the first constitution of things they are directly from God. And since there can be no transmutation from the potential to the actual in simple creation, we must admit that, in respect of its proper cause, matter is subject at command to God only, and that the forms of bodies are from God.
- text taken from Compendium of the Summa Theologica of Saint Thomas Aquinas, by Bishop Berardus Bongiovanni