Proslogium and Monologium/Monologium/Chapter9
Those things which were created from nothing had an existence before their creation in the thought of the Creator.
But I seem to see a truth that compels me to distinguish carefully in what sense those things which were created may be said to have been nothing before their creation. For, in no wise can anything conceivably be created by any, unless there is, in the mind of the creative agent, some example, as it were, or (as is more fittingly supposed) some model, or likeness, or rule. It is evident, then, that before the world was created, it was in the thought of the supreme Nature, what, and of what sort, and how, it should be. Hence, although it is clear that the being that were created were nothing before their creation, to this extent, that they were not what they now are, nor was there anything whence they should be created, yet they were not nothing, so far as the creator's thought is concerned, through which, and according to which, they were created.