God’s glory is his character.
What defines his character? A holy, self-disregarding helpfulness.
Holiness is not a character quality alongside things such as patience, kindness, or gentleness. It has to do with how close to perfection a particular character quality is. The closer that quality gets to being perfect, the more it can be said to be holy.
In other words, holiness means that a given quality is so quantitatively different that it appears to be qualitatively different. For example, a good person who is holy is so thoroughly good that their goodness seems to be of a different kind. It is still goodness by virtually anyone’s definition, but it’s radical. It’s far beyond anything else we would consider good. That is to say, it’s holy.
So to say that God’s character — his self-disregarding helpfulness — is holy is to imply that we will never be able to fathom the depths of how completely he self-effacingly attends to the wellbeing of his creation.
Purity means singularity of motive. And because God is perfectly pure, we could say that he has only one motive behind all he does, and that is to fill all sentient life with the joy of being as he is, self-disregardingly helpful.
So to sum up, God is self-disregarding helpfulness to a radical degree. That is his glory.
In everything he does, his purpose is to make us as he is. When he seeks his glory, this is what he has in mind.
And whenever God has his way and someone does, in fact, become a little bit more self-disregardingly helpful, God is glorified.
