Recent discussions call to mind two distinctions that are sometimes helpful.
One is the distinction between distinction and separability. That two things are not separable -- that you can't have one without the other -- does not mean that they cannot be distinguished. The two sides of a coin, for example, cannot be separated1, but they can certainly be distinguished.
The other is the distinction between two meanings of the question, "What does this mean?" One meaning, which you might call the proximate meaning, is simply the literal sense of whatever the "this" is; the second (remote) meaning is what follows from the truth of the literal sense. You've seen, perhaps, the "Far Side" cartoon of the two fishermen on a lake, with mushroom clouds rising from beyond the mountains. The proximate meaning of those clouds is that a nuclear war has destroyed civilization. The remote meaning is expressed by one of the fishermen: "I'll tell you what this means, Norm -- no size restrictions and screw the limit!"
The first distinction would apply when discussing the names of God. In His simplicity, God is His essence and His existence (on a good day, I can make some sense out of that). Not only are God's justice and mercy inseparable, God is both His justice and His mercy. Nonetheless, we can distinguish between His justice and His mercy2, and still more between justice and mercy as creation participates in them.
The second distinction would apply in the ongoing look at the question, "What does 'God is love' mean?" The proximate metaphysical and theological meaning of the statement, "God is love," is definitely one worth exploring. But it's perhaps noteworthy that in the encyclical called "God is Love," Pope Benedict XVI is not much concerned with this proximate meaning. The letter is really about what follows from what follows from the fact that God is love, which is to say, it's about what follows from the fact that God loves.
Certainly our understanding of the remote meaning reflects back on our understanding of the proximate meaning, but love more than any other matter for reflection is something that must end in action. In bumper sticker terms, love is act, not fact.
1. Yes, you could get a precision saw and cut the coin in half, but that effectively destroys the coin, and even then you'd be left with two coins, each with two sides.
2. You can even oppose God's justice and mercy, as Pope Benedict does in Deus Caritas Est 10: "God's passionate love for his people—for humanity—is at the same time a forgiving love. It is so great that it turns God against himself, his love against his justice." But such opposition is conceptual; the Pope continues, "Here Christians can see a dim prefigurement of the mystery of the Cross: so great is God's love for man that by becoming man he follows him even into death, and so reconciles justice and love."