Bonaventure works up to a description of the Trinity by contemplating what it means for God to be good.  Good is self-diffiusive, and the highest good must be supremely so.  Supreme self-diffusion must involve the complete gift of one’s entire being to another, which is what the Father diffuses to the Son.  Perfect goodness must produce what is “actual and substantial, and a hypostasis as noble as the producer.  Following Richard of St. Victor, he says that this must have a triune character: “from an eternal principle eternally coproducing so that there would be a beloved and a cobeloeved, the one generated and the other spirated.

Then he expounds with mystical excitement on the mystery (I am using the translation of Ewert Cousins, found in Bonaventure: The Soul’s Journey into God, the Tree of Life, the Life of St. Francis (The Classics of Western Spirituality) :

“If, therefore, you can behold with your mind’s eye

The purity of goodness,

Which is the pure act

Of a principle loving in charity

With a love

Tat is both free and due and a mixture of both,

Which is the fullest diffusion by way of nature and will,

Which is a diffusion by way of the Word,

In which all things are said,

And by way of the Gift, in which other gifts are given,

Then you can see

That through the highest communicability of the good,

There must be

A Trinity of the Father and the Son and the Holy Spirit.

From supreme goodness,

It is necessary that there by in the Persons

Supreme communicability;

From supreme communicability, supreme consubstantiality;

From supreme consubstantiality, supreme configurability;

And from these supreme coequality

And hence supreme coeternity;

Finally from all of the above, supreme mutual intimacy,

By which one is necessarily in the other

By supreme interpenetration

And one acts with the other

In absolute lack of division,

Of the substance, power and operation

Of the most blessed Trinity itself.”

If we think we’ve understood that, Bonaventure reminds us that we have been contemplating God only from the perspective of one of the cherubim, and that in addition to the amazement of God’s supreme “co-” attributes, we must consider the persons:

“For here is

Supreme communicability with individuality of persons,

Supreme consubstantiality with plurality of hypostases,

Supreme configurability with distinct personality,

Supreme coequality with degree

Supreme coeternity with emanation,

Supreme mutual intimacy with mission . . . .

For if there is here

Supreme communication and true diffusion,

There is also here

True origin and true distinction;

And because the whole is communicated and not merely part,

Whatever is possessed is given,

And given completely.

Therefore, the one emanating and the one producing

Are distinguished by their properties

And are one in essence.”

The two cherubim’s perspectives are thus complementary.  On the one hand: “if you are the Cherub, [you contemplate] God’s essential attributes, and if you are amazed because the divine Being is both first and last, eternal and most present, utterly simple and the greatest or boundless, totally present everywhere and nowhere contained, most actual and never moved, most perfect and having nothing superfluous or lacking, and yet immense and infinite without bounds, supremely one and yet all-inclusive, containing all things in himself, being all power, all truth, all goodness.”

On the other hand, “if you are the other Cherub, [you contemplate] the properties of the Persons, and you are amazed that communicability exists with individuality, consubstantiality with plurality, configurability with personality, coequality with order, coeternity with production, mutual intimacy with sending forth.”