Every cause acts through some form and produces its effect which is in a way like its form; and therefore the form of the effect must be comprehended by the cause. As God is the cause of all, necessarily the forms of all are in Him. God is therefore in essence omniform. Hence the Orphic saying: "Jupiter, form of all." In pure potency, which is matter, exist all the natural forms confusedly and potentially. Similarly, in pure act, which is God, exist all the forms distinctly and actually. But, really, are these forms differentiated in God as they would be in the way of nature, just as light, heat, dryness and lightness are in fire; and does He act through them prompted by some necessity of His nature? Certainly not.
"Form" here does not imply a commonality of nature, since something is obviously capable of engendering or creating something else of unlike nature. Rather it means the principle of something coming into being. Perhaps this could be understood with less confusion if the Greek concept of "energy" were employed. Every cause acts through its energy, an energy ordered to its effect. God created the world with His infinite uncreated Energies, which exist in Him undifferentiated, distinctly, and actually.