(Read this as Lectio — it cannot be read quickly without reflection.)
What is God? That without which nothing exists. Just as nothing can exist without him, so he cannot exist without himself: he exists for himself, he exists for all, and consequently in some way he alone exists who is his own existence and that of all else.
What is God? The Beginning; this is the answer he gave of himself. Many things in the world are spoken of as beginnings, and this is in respect to what comes after them. Yet if you look back and see something which precedes another, you will call that the beginning. Therefore, if you seek the true and absolute beginning, you must discover that which has no beginning. That from which everything began clearly had no beginning itself, for if it began, it must have begun from some source. For nothing begins from itself, unless someone thinks that something which does not exist can cause itself to be or that something existed before it came to be, but since reason approves of neither of these it is clear that nothing exists as its own beginning. Moreover, what had its beginning from another was not first. Therefore, the true beginning in no way had a beginning, but totally began from itself.
What is God?
A being for whom the ages have neither approached nor departed, and yet are not coeternal.
What is God?
‘From whom and through whom and in whom are all things.’
From whom are all things through creation, not as from a source;
Through whom are all things, lest you think there is one who is the author and one who is the maker; in whom are all things, not as in a place but as in power.
From which are all things as if from one beginning; the author of all; through whom are all things, lest we think the maker a second beginning; in whom are all things, lest a third reality be introduced, that of place.
From whom are all things, not of whom, because God is not matter; he is the efficient not the material cause. In vain do philosophers seek the material: God had no need of matter. He did not seek a workshop or a craftsman. He made everything through himself, in himself. Out of what? Out of nothing; for if he made it from something, he did not make that and consequently did not make everything. Do not suppose that from his own uncorrupted and incorruptible substance he made so many things, for even if they are good, they are corruptible.
St. Bernard of Clairvaux
On the Song of Songs