"Kolokotronis, on the Erasmus thread you posted something from the Holy Father (or perhaps from then Cardinal Ratzinger) about the Holy Ghost proceeding from the mutual longing between the Father and the Son. You said it was from Deus Caritas Est, but I do not see it there. Do you rememeber what I am talking about?"
I don't remember it as coming from +BXVI but rather from +Gregory Palamas, who, as you may know, His Holiness is both familiar with and fond of quoting. This is likely the passge, which is from his Topics of Natural and Theologic Science (it also explains the idea of "procession" and how we can receive the Spirit "through" the Son:
"The Spirit of the supreme Logos is a kind of ineffable yet intense longing or 'eros' experienced by the Begetter for the Logos born ineffably from Him, a longing experienced also by the beloved Logos and Son of the Father for His Begetter; but the Logos possesses this love by virtue of the fact that it comes from the Father in the very act through which He comes from the Father, and it resides co-naturally in Him.
It is from the Logos's discourse with us through His incarnation that we have learned what is the name of the Spirit's distinct mode of coming to be from the Father and that the Spirit belongs not only to the Father but also to the Logos. For He says 'the Spirit of Truth, who proceeds from the Father' (John 15:26), so that we may know that from the Father comes not solely the Logos - who is begotten from the Father - but also the Spirit who proceeds from the Father. Yet the Spirit belongs also to the Son, who receives Him from the Father as the Spirit of Truth, Wisdom and Logos. For Truth and Wisdom constitute a Logos that befits His Begetter, a Logos that rejoices with the Father as the Father rejoices in Him.
This accords with the words that He spoke through Solomon:'I was She who rejoiced together with Him' (Prov. 8:30). Solomon did not say simply 'rejoiced' but 'rejoiced together with'. This pre-eternal rejoicing of the Father and the Son is the Holy Spirit who, as I said, is common to both, which explains why He is sent from both to those who are worthy. Yet the Spirit has His existence from the Father alone, and hence He proceeds as regards His existence only from the Father. Our intellect, because created in God's image, possesses likewise the image of this sublime Eros or intense longing - an image expressed in the love experienced by the intellect for the spiritual knowledge that originates from it and continually abides in it."
Yes, that is it. I remembered wrong. Thank you.