All analogies and pictures fall short in trying to capture the Trinity. The three points to uphold simultaneously are:
- God is three persons.
- Each person is fully God.
- There is one God.
Nevertheless, I thought that Grudem had some good insight about there being at least some measure of combination of unity and diversity not just in God, but even in some parts of his creation, namely, marriage. He writes:
"Because God in himself has both unity and diversity, it is not surprising that unity and diversity are also reflected in the human relationships he has established. We see this first in marriage. When God created man in his own image, he did not create merely isolated individuals, but Scripture tells us, "male and female he created them" (Gen. 1:27). And in the unity of marriage (see Gen. 2:24) we see, not a triunity as with God, but at least a remarkable unity of two persons, persons who remain distinct individuals yet also become one in body, mind, and spirit (cf. 1 Cor. 6:16-20; Eph. 5:31)."
I'm not sure where he gets the "one in body, mind, and spirit" from exactly, but for sure there is at least a real union there in some ways. He then goes on to point out similarities in this thing of submission and authority, which is also interesting:
"In fact, in the relationship between man and woman in marriage we see also a picture of the relationship between the Father and Son in the Trinity. Paul says, "But I want you to understand that the head of every man is Christ, the head of a woman is her husband, and the head of Christ is God" (1 Cor. 11:3). Here, just as the Father has authority over the Son in the Trinity, so the husband has authority over the wife in marriage. The husband's role is parallel to that of God the Father and the wife's role is parallel to that of God the Son. Moreover, just as Father and Son are equal in deity and importance and personhood, so the husband and wife are equal in humanity and importance and personhood."I've never actually heard any teaching on the union of man and wife (or even personal comment for that matter! ... unless I've forgotten). But it's interesting that the bible does seem to have this unity/diversity category in marriage as well as with the nature of God himself. Perhaps then it's not right to think of the Trinity as something that is altogether alien to human experience, even if in its totality it can't be captured in an analogy.