In this paper, I question a widespread reading of a passage in the last part of the Phaedrus dealing with the science of dialectic. According to this reading, the passage announces a new method peculiar to the later Plato aiming at defining natural kinds. I show that the Phaedrus itself does not support such a reading. As an alternative reading, I suggest that the science of dialectic, as discussed in the passage, must be seen as dealing primarily with philosophical rhetoric and knowledge of human souls.