Proslogium and Monologium/Monologium/Chapter5

Chapter V
Just as this Nature exists through itself, and other beings through it, so it derives existence from itself, and other beings from it.

Seeing, then, that the truth already discovered has been satisfactorily demonstrated, it is profitable to examine whether this Nature, and all things that have any existence, derive existence from no other source than it, just as they do not exist except through it.

But it is clear that one may say, that what derives existence from something exists through the same thing; and what exists through something also derives existence from it. For instance, what derives existence from matter, and exists through the artificer, may also be said to exist through matter, and to derive existence from the artificer, since it exists through both, and derives existence from both. That is, it is endowed with existence by both, although it exists through matter and from the artificer in another sense than that in which it exists through, and from, the artificer.

It follows, then, that just as all existing beings are what they are, through the supreme Nature, and as that Nature exists through itself, but other beings through another than themselves, so all existing beings derive existence from this supreme Nature. And therefore, this Nature derives existence from itself, but other beings from it.