There are times when someone else has said something so well, it is better to let them speak on the matter and add a bit of commentary.
Hans Kung does not dismiss the ambiguous notion of God of some philosophy, agnostics, and the spiritual but not religious, but he does suggest there is more to be known about God than vague apophatic impressions. As a Christian this is revealed for him in the person of Jesus, by whom it is implied we can evaluate and contextualize what had been said before about God in the Old Testament. In Why I Am Still a Christian, he writes:
[T]he God of the Judeo-Christian faith unambiguously proves to be a God, not against humanity but for humanity. 'Immanuel: God with us'... a God of liberation, of mercy, of salvation, of grace... This one and only God* is that one very last, very first reality which, together with Christians and Jews, Moslems also worship as Allah... He is the reality that Hindus seek in Brahma and Buddhists seek in the Absolute Dharma (Nirvana)* as do the Chinese in heaven or the Tao...
This is certainly the biblical God, but the biblical God perceived in the new view of the world according to Copernicus, Galileo and Darwin. A God who, as the all-embracing and all-pervasive God of the world, is certainly not a person in the way a human being is a person... God burst apart the concept of a person; God is more than a person.
But conversely, a God who is the foundation of the personal nature of human beings cannot himself be a-personal either. He is not sub-personal. God also bursts apart the concept of the impersonal; God in not less than a person either.
I can appreciate the objection of that God isn't necessary to explain our nature, that it is the result of evolution (which is the result of physics) and the choices of those around us and our own, but what he is getting at here is more fundamental. It is a reference to the fundamental nature of reality. No matter how far we push back the causal chain, there is still no particular reason why certain phenomena should have the qualities they do.
These qualities can be described and modeled and explained as the result of other phenomena, but these explanations can at best only depend on the qualities of the phenomena to which the phenomena under investigation are reduced, and to which those are reduced and so on ad infinitum.
So it can be said that these qualities are just the outcome of the natural laws of the universe, which are the major themes of the collective descriptions of regularly occurring empirical phenomena studied by science. But it is still dependent on what is already there. If God is the source, substance and sustainer of existence rather than merely a first cause for (a) universe, then such laws, phenomena and qualities are indeed aspects of the divine, and therefore foundation to our personal nature.
Kung also discusses the idea of paradox, and I would add that his always happens when we push our dualistic categories to their conceptual limit. They are after all just models and descriptions, and cannot contain the fullness of reality. This is also relevant for other related divine paradoxes such as God's transcendence and immanence but to stay on the more refined point and return to Kuhn's writing:
[E]ven though this God is 'super-personal', he is still a genuine partner who is kind and absolutely reliable, a partner to whom we can speak. Of course we can only talk about this God, and talk to him, in metaphors and images, in cyphers and symbols. But we can nonetheless communicate with him with human words -- how else? And it is obviously on this basis that this possibility of prayer and worship depends...
I would suggest that meditation and contemplative prayer can be added to the list, but they are also expressions of human faculties. To continue:
For in simple prayer and genuine worship even modern men and women can find certain values at a wholly different depth of their existence, and can truly experience where we come from, where we are, and where we are going.
This last part is important for appreciating how the unknown God of the sort-of-spiritual and abstract theology is associated with what we think of as personal qualities such as compassion and grace.
In The Beginning of All Things, Kuhn summarizes these same points and elaborates:
[God] is not a limited individual among other persons. God is not a super-person and a superego.
Precisely because God is not a "thing", precisely because, as is emphasized in Eastern wisdom*, he cannot be understood, seen, manipulated; because is not at our disposal, he is also not impersonal, subpersonal.In other words, God defies our notions and the categories which they spawn. It is no more appropriate to label God a person than it is to think of God as impersonal or a non-person, as some vague cosmic force. There are many ways to understand God, and many names with which to call on God, but there is no formula or equation or model in which God can be contained. We should not disparage those whose partial understanding of God differs from our own incomplete notions nor despise the differences in our perspectives. Rather we should celebrate the many ways we have to know the divine.
Spinoza's identification of God with nature and the laws of nature does not solve any problems... natural laws such as physicists are tempted to assume on the basis of their particular and limited method cannot explain the whole of reality.
This is not just the view of the Bible and the Qur'an; most Buddhists also accept an Ultimate Reality. And this is more than the cosmos: more than a universal reason or a great anonymous consciousness. It is more than the supreme idea (Plato) or a thinking related to itself and thinking about itself (Aristotle). It is more than the pure beauty of the cosmos or the blind justice of history. The Ultimate Reality is not indifferent to us and does not leave us indifferent, but is our "ultimate concern", as Paul Tillich put it...
*I knew Kung has repeatedly used the phrase "God is not less than a person", and when I searched for a source to quote this and explore the idea more fully I found this, which mirrors what has been said here recently. How about that? I guess if I am wrong I am in some distinguished company.