When Marsilio Ficino arrives at his banquet-fiction as the ninth and last guest, he claims thereby just to fulfil the host’s wish that there should be nine Platonic guests ‘so that the number of Muses might be achieved’. But while the number of Muses naturally is of consequence, Ficino’s arrival in the first chapter of the De amore (1469) announces more than his indebtedness to the nine sisters of Mount Helicon, namely, the vast significance of numbers in his theory of love. It was probably no coincidence that Ficino in his reworking of Plato’s Symposium chose to arrive under the wondrous number nine, associated with Dante’s beloved Beatrice in the Vita nova. This paper  presents the crucial numbers of Ficino’s De amore, and attempt to use them as a guide to his theory of love.