Trinitarian Theology is, perhaps, the one area that is, as it is officially expressed today, transparently relational. God's revelation to Moses, for example, is characteristically relational.
"But," said Moses to God, "when I go to the Israelites and say to them, 'The God of your fathers has sent me to you,' if they ask me, 'What is his name?' what am I to tell them?" God replied, "I am who am." Then he added, "This is what you shall tell the Israelites: I AM sent me to you." [Exodus 3:13-14; NAB translation]
It is possible to glean from this more than one relational predicate of God, bearing in mind that pure logic is not fully capable of expressing existence, per se.
Each of these predicates is relational in some sense. The first predicate asserts a relationship between God and reality, the set of all things that exist. The second predicate negates a relationship between God and each other member of reality. The third predicate asserts a relationship of uniqueness.
It seems to me that each of these predicates, or something very like them, is implied in God's revelation to Moses, and, indeed, his revelation may contain much more (such as eternal, unchanging existence), all in four pictographic terms.
Note: one translation given in the CCC on the Vatican web site is "I AM WHO I AM." [See ¶ 205.] It seems to me this translation presents a vacuous meaning, as distinguished from "I AM WHO AM." "I am who I am." is true of everybody, and, as such, is not a particularly interesting statement, even when every word is written in capital letters. Furthermore, it is not fully consistent with God's next statement, "This is what you shall tell the Israelites: I AM sent me to you." I've heard of other possible translations, such as "I AM THAT I AM." This translation, unfortunately, fails to capture the uniqueness property. It seems to me this is probably nothing more than an inaccuracy in the English. The rest of the CCC on this makes it clear that God is "HE WHO IS," as opposed to the more vacuous "HE WHO IS WHO HE IS."
God's predicates have a special quality. It is insufficient, for example, to say that God is superlatively powerful, merciful, loving, etc. Tradition attaches the qualifier "all" to these predicates. What does "all" mean, however. It seems to me that it can mean two things in ordinary conversation. To say that someone is "all thumbs," for example, suggests that their manual dexterity is "challenged" because their thumbs dominate so much they get in the way. There is a suggestion in this direction even when we way someone is "all heart," and this is decidedly what we mean when we say someone is "all brawn and no brains." In that sense, we wouldn't accuse God of being "all" anything. Rather, when we say God is "all powerful" or "all loving" we mean that God is so superlatively these things that nothing greater can be conceived.
We also say, using the same word "all," that God is "the source from whom all being flows." This claim also applies to God's predicates. God is the source from whom all power, love, knowledge, understanding, goodness, truth, beauty, mercy, justice, etc. flows, and not just at this moment, but existentially, for all time and all place.
These predicates can, in some sense, be subsumed in the predicate "good." God is "The Good." Indeed, the predicates belong together (and, indeed, are inseparable) precisely because they fill out the meaning of "good" in God.
Jesus alluded to these two senses of "all" when he said, "I am the Alpha and the Omega." To say that God is the source of all goodness is to say he is the Alpha. In the same way, to say that he is the greatest good that can be conceived, either now or ever, is to suggest he is the Omega of goodness. This relationship parallels the relationship between Eros and Agape love studied so admirably in Pope Benedict XVI's encyclical "God is Love." Agape love is love that "issues forth," while Eros love is love that "draws toward."
¶ 210 and 211 of the CCC introduce God's mercy and graciousness. To say that God is merciful and gracious presumes that God exists in a relationship of power to others. This is implied by the fact that all beings stand in a relationship of existential dependence on God. God graciously wills all beings to exist. Thus, this existential dependence says something about God's will and our relationship to it. Furthermore, the graciousness of God's will is already expressed, in some measure, by the claim that existence itself is something positive that God freely chooses to give. His gracious will, however, extends to a relationship of nurturing. God nurtures our spirits, and lifts us up out of the darkness of our narrow concupiscence and self-absorption.
Together with his mercy, God's graciousness places him in a more deeply personal relationship with us. He is not simply an abstract target to aspire to, or an abstract judge of our moral limitations. This perspective on our relationship to God gives us a "warm fuzzy" the way nothing else can. God is not simply "God" or the "I AM." He is "Abba!" These predicates of God, more than any others, help us to believe the reality that we are His "children" made in His image and likeness.
Thus, the predicate "Father" or "Abba" cannot be over-estimated in its importance to us. It is a subsuming predicate, comparable in some ways to "Good," but it is a deeply personal predicate, and thus a highly complex and subtle one. Like the other predicates, however, it is both a "source" and a "sink." God's "Fatherhood" is both the source and the model of all other fatherhood.