Ah, the feast of Basil and Gregory (Nanzianzen). For some reason, Basil's brother Gregory (of Nyssa, also a "Cappadocian Father") does not get honored today, too. We owe these three great theologians a lot for preserving the faith in the divinity and humanity (both! whole and entire! at the same time!) of Jesus at the time of the Arian heresy. Basil the Great wrote a wonderful treatise on the Blessed Trinity, one which I really found helpful in prayer, once someone helped me understand what on earth he was doing in a section that seemed to be more about mathematics than religion. For some things, you really need a teacher. At any rate, it's that book that makes Basil (and not his lifelong friend Gregory, and not even his outstanding brother Gregory) my favorite Cappadocian.