It is in this respect that Socrates, as well as all ancient philosophy, can be said to be rationalist. It is rationalist in the sense that reason, the logos or intellectual faculty, is unhindered by raw and unbridled, bacchic passions. In no way can ancient philosophy, including cosmology and physics, be considered a positivist science in the modern sense.
Then the speeches start. These proceed from the lower to the higher, from love as a physical attraction paving the way to virtue of the mind (Phaedrus and Pausanias), ascending with Eryximachus into a physiological and cosmic force present in and moving all things, then, with Aristophanes, entering the sphere of ætiology and mythology (told in a creation-fall-redemption pattern) explaining Love as a desire for completeness and wholeness, and therefore not primarily physiological and sexual in nature, finally moving through, with Agathon, to the essence of Love, what it is (namely, it is the beautiful and virtue). These speeches are all worthy and possess much poetry, yet there is something missing or not up to the point in them. They pave the way to the climax, Socrates’ speech.
Then comes Socrates’ critique of Agathon’s speech. It is one of two places where we openly meet Plato’s famous dialectics. Dialectics (the confrontation of two or more different, often contradictory hypotheses to infer a conclusion—a truth) is the other way in which Socrates, Plato, and their succesors can be said to be rationalists. Again, it is very different from cartesian doubt. We will return to this below.
Socrates, shortly after starting his speech, introduces another character, a foreign prophetess named Diotima (said to be from Mantinea, a place name in the Peloponnesus phonetically so close to manteia, μαντεία–-power of divination, oracle—that it cannot be mere coincidence). That Socrates was guided by a diviner is telling. From here on till the end of his speech, he essentially recounts Diotima’s own words. This adds yet another level of separation from the reader to the ones observed above. The fact that Diotima, from 207a, speaks alone, without recourse to dialectics is also significant. It places the entire speech within the sphere of spiritual contemplation. When one enters the higher mysteries, traditional philosophical language no longer suffices. Dialectics is a way to produce opinions, which may or may not be close to truth. When one contemplates Truth itself, dialectics is therefore useless. Direct experience alone allows one to access the higher spheres of reality. Such experience produces awe and “wonder” (208b). Diotima’s teachings to Socrates is the closest thing to a divine revelation that we know from pre-Christian Antiquity. It anticipates in certain ways the concept of theological discourse that would become prominent in Christian times and reach its highest form with the Cappadocian fathers. It would perhaps not be wrong to see in Christian writers and orators, in so far as they conveyed the logos of God, the successors of Socrates and Diotima.
