(This is a simplified version of process theism, but it's also a bit Tillichian, a bit Hegelian, a bit Patristic, a bit Radically Orthodox, a bit postmodern, all at once.)
I experience myself and others within our continually differing inclusion.*
This experience, I'm convinced, is inescapable and fundamental. To deny it is either inattentive or self-deceptive. Its inescapability is its evidence.
And the categories—self, others and our continually differing inclusion—are more basic than any other categories. Any worldview that neglects any or all of them is inadequate and anti-empirical.
Even physics, which requires physicists, must presuppose these categories. All physicists, whether they notice or not, experience themselves and others—including the smallest and largest "others" they study—within their continually differing inclusion. These categories are experienced as operative whenever the field of physics happens, or whenever any other scientific field happens. They're experientially inescapable. If you cringe at calling them metaphysical categories, try calling them "protophysical."
I never experience these categories—self, others and our continually differing inclusion—in exactly the same way. My experience of myself is never exactly the same, my experience of others is never exactly the same, and my experience of our inclusion is never exactly the same.
So while these categories continue in every moment, they continue differently in every moment. That they continue never changes; how they continue always changes. They are in a process of continual, mutual renewal.
This is a form of process thought, which dares to view everything, even the tiniest bits and largest masses of everything, in terms of the continually differing inclusion of continually differing selves and others, extrapolating from these categories' experienced inescapability.
The continually differing inclusion of continually differing selves and others is also experienced as boundless. With St. Paul, I would call this boundless, continually differing inclusion God.** All continually differing selves and others have traditionally been said to arise from God, through God and in God (Romans 11:36), their boundless, continually differing inclusion. According to the Nicene Creed, even God is, boundlessly, the continually differing self-inclusion of God's continually differing self-othering (God originating God, God inclusively differing from God, God differently including God).***
Our boundless, continually differing inclusion includes the personal and the impersonal, and thus cannot be reduced to either of these categories. (That, again, is what the Christian doctrine of the Trinity implies—God is not personal without being interpersonal.)
Faith is letting myself be drawn into this boundless, continually differing inclusion, trusting this as my and all others' ultimate good.
Unfaith, sin, is fleeing (self-deceptively and unsuccessfully) from this boundless, continually differing inclusion, fearing this as my ultimate bane, denying its undeniability.
Christian faith is letting myself be drawn into this boundless, continually differing inclusion, renewingly practiced in the Body of Christ, begun with Jesus of Nazareth, whose human, continually differing inclusion of continually differing selves and others still embraces and outlives all powers of destruction.
*"The primitive stage of [categorizing] … is the vague grasp of reality, dissecting it into a threefold scheme, namely, "The Whole," "That Other," and "This-My-Self." ... This is primarily a dim division.… There is the vague sense of many which are one; and of one which includes the many. ... There is the feeling of the ego, the others, the totality. This is the vague, basic presentation of the differentiation of existence... We are, each of us, one among others; and all of us are embraced in the unity of the whole."—Alfred North Whitehead, Modes of Thought (New York: Simon & Schuster, 1968 ), p. 110.
**"[In our experience of God,] God can never be object without being at the same time subject. ... The same experience expressed in abstract language is the disappearance of the ordinary subject-object scheme in the experience of the ultimate, the unconditional. In the act of faith that which is the source of this act is present beyond the cleavage of subject and object. It is present as both and beyond both."—Paul Tillich, Dynamics of Faith (New York: HarperCollins, 1957), pp. 12-13. "The unity of a transcendent universe, and the multiplicity of realized actualities, both enter into our experience by [a] sense of deity... We owe to the sense of deity the obviousness of the many actualities of the world, and the obviousness of the unity of the world."—Whitehead, p. 102
***"God is the mystery of a gift exchanged, and non-identically repeated. That is the mystery of the Trinity. God is not a being, but Being as such. But Being as such is word and gift as well as origin; it is community and not isolated individuality."—Catherine Pickstock, “Is Orthodoxy Radical?” http://www.affirmingcatholicism.org.uk