Q: Philosophers have long noted that God is many things, particularly being, truth, beauty, goodness, and unity or oneness. What is the typical reaction of a philosopher upon hearing that “God is love”? How might a philosopher understand this concept?
Monsignor Sokolowski: It would be hard to say that “God is love” apart from the doctrine of the Holy Trinity. Even if one were to think that the deity is benevolent, one could still not say that it is love. That sort of divine love would be relative and not substantial in the deity. Only because the Father gives everything to the Son, and because the Son and Father express their love in the Holy Spirit, can one say, with St. John, that God is love. I don’t see how such an understanding of God could have arisen in philosophical thinking. (http://www.zenit.org/article-15295?l=english)
This seems like an odd position to take. St. Thomas in the Prima Pars shows from reason that God has intellect and will. The first formation of the will by the good is love. Since, therefore, God is his own good and knows that he is, his will desires his own essence. This desire is nothing other than love; but, because of divine simplicity, God is everything which he has. Therefore, it is necessary that God is love.
This may seem tantamount to proving the Trinity, since the procession according to will is the common spiration of the Holy Spirit; but, as St. Thomas points out:
Nor is the image in our mind an adequate proof in the case ofGod, forasmuch as the intellect is not in God and ourselves univocally. Hence, Augustine says (Tract. xxvii. in Joan.) that by faith we arrive at knowledge, and not conversely.
Thus, even knowing that God is love is not sufficient for demonstrating the existence of the Trinity, because we only know that there is a divine will and not whether that will knows through a term distinct form the divine essence which terminates the action of will. Unless we know this, we do not know the distinction between the persons. (Although we may be able to form right opinion about it.)