As for the doctrine of “gnosis,” its adherents rank among the greatest perpetrators of polytheism, deception, and sheer calumny. One of their so-called “knowers” declares:
“On the seeker’s first steps he distinguishes between obedience and sin—looking at the divine command. Then he beholds obedience without sin—looking at the divine decree. Finally he sees neither obedience nor sin at all—because, in his view, existence is but a single reality.”
They fail to differentiate between that which is one in essence and that which is merely one in kind, for all created things share the bare name “existence.” Yet existence itself is of various sorts: that which subsists by itself and that which subsists through another; that which is necessary in itself and that which is contingent in itself.
Just as all animals share the term “animal,” and all human beings share the term “human,” it is self-evident that the very existence of this particular man is not the very existence of that horse. Indeed, the existence, animality, and humanity of one creature are not identical to the existence, animality, and humanity of another. Rather, there is only a shared aspect in which they resemble one another, sometimes called a universal, an absolute, or a common measure. Such a universal, however, has no external, all-embracing existence outside the mind; it is found only as something specified and individuated.
Thus every existent possesses a reality unique to itself, which no other shares. In the external world there is no single entity that two beings hold in common; they merely resemble one another—this one mirrors that, and that mirrors this—while each is distinguished in its essence and attributes from all else. How much more transcendent, then, is the Creator, glorified and exalted be He!
All of this is treated at length elsewhere with the detail it deserves.