This paper analyses chapter 58 of Theophrastus’ De sensibus, where Democritus’ account of phronein is famously presented. Democritus traces phronein to symmetria of the soul, that is conceived, in turn, as a state of thermic equilibrium, depending on his consideration of psyche as an aggregate of spherical and thin atoms flowing throughout the body and giving it life, movement, and perception. As a consequence, according to him, psychic states go hand in hand with changes in the body. In the following (...) section of this paper, I offer additional evidence in favor of the controversial manuscript reading μετὰ τὴν κίνησιν. As a result, a consistent theory by Democritus can be reconstructed, according to which the balanced state of mobility and temperature of the psychic atoms concentrated in the head that generates a correct thinking necessarily follows the movement of sensible eidola throughout the body. In fact, a number of passages from Hippocratic writings attest that Democritus shared the key features of this explanation with the physiological and medical approach of the time. (shrink)