In his treatise Contra Gentiles , Athanasius reproduces an argument from the Phaedrus that provides the immortality of the soul. Anything that has to be moved by something else is mortal and finite; whatever moves of itself is immortal, and immortally mobile. What is most fully mobile is what is unoriginated and imperishable.
Likewise, in the Sophistes , Plato says that the realm of being is the realm of life and movement. That is, the realm of ideas is not static, but supremely alive and active.
