Monologion: Chapter 26
BASIC WRITINGS
Therefore, just as the supreme nature never yields a place in his simplicity for accidents that bring about change, in the same way he does not reject being sometimes described in accordance with those accidents that in no way oppose his supreme immutability. And yet his essence is not subject to any accident by which it can be understood to be changeable.From this it can also be concluded that he is not susceptible of any accident. For surely those accidents that cause a change in something by beginning or ceasing to be present in it are judged, in virtue of that very effect, to be truly accidents of the thing they change; and by the same token, those that lack a similar effect are perceived to be improperly called accidents.Therefore, just as he is always in every respect the same as himself substantially, so he is never in any respect different from himself, even accidentally. But however things stand with the proper use of the word 'accident', it is undoubtedly true that nothing can be said of the supremely unchangeable nature from which he could be understood to be changeable.
Chapter 26 In what sense he is to be called a substance, and that he is beyond every substance, and uniquely is whatever he is
But if what I have observed about the simplicity of this nature is certain, in what sense is he a substance? For although every substance is capable of taking on an admixture of differences or a change from accidents, his unchangeable purity is altogether inaccessible to admixture or change. Therefore, how will it be the case that he is a substance at all, unless 'substance' is used to mean
'essence',35 and he is just as much beyond as he is above every substance? For however great the difference is between the being who is through himself whatever he is and makes every other being from nothing, and a being that through another is made from nothing to be whatever it is, the difference is every bit as great between the supreme substance and those that are not the same thing that he is. And since he alone among all natures has from himself whatever existence he has, without the help of any other nature, is he not uniquely whatever he is, having nothing in common with his creatures? Accordingly, if any word is ever applied to him in common with others, it must undoubtedly be understood to have a very different signification.
35 Anselm's point here is that we cannot call God a substance in the sense in which a substance is distinguished from its accidents. But we can use the word 'substance' as interchangeable with 'essence', in which case God is indeed a substance (that is, an essence or being) that is beyond and above all other substances.