It is a great thing to advance to intelligible things; it is a great thing to advance to spiritual things; it is a great thing for your heart to reach the knowledge that there is something that is not extended in space and does not vary in time. What does wisdom look like? Who is able to ponder it? Is it long? Is it square? Is it round? Is it here in one way and there in another? Someone ponders it in the East, someone else in the West: if they both think well about it, it is completely present to both of them despite how far apart they are. What is this? Who can grasp it? Who grasps that substance, that divine and immutable nature? Don’t be in such a hurry! You will one day become able to grasp it.! (EnPs 146[147], 14; PL 37, 1908)

Perhaps those last sentences reflect Augustine’s own journey. In several writings he described how long and how winding was the road he took before he was able to conceive of something being without being a body. Bernard Lonergan wrote his great book Insight, as a guide to bring readers to the same insight:

St. Augustine of Hippo narrates that it took him years to make the discovery that the name, real, might have a different connotation from the name, body. Or, to bring the point nearer home, one might say that it has taken modern science four centuries to make the discovery that the objects of its inquiry need not be imaginable entities moving through imaginable processes in an imaginable space-time. The fact that a Plato attempted to communicate through his dialogues, the fact that an Augustine eventually learnt from the writers whom, rather generally, he refers to as Platonists, has lost its antique flavour and its apparent irrelevance to the modern mind. Even before Einstein and Heisenberg it was clear enough that the world described by scientists was strangely different from the world depicted by artists and inhabited by men of common sense. But it was left to twentieth-century physicists to envisage the possibility that the objects of their science were to be reached only by severing the umbilical cord that tied them to the maternal imagination of man (Insight, p. xx-xxi).

For Augustine, see Confessions, IV, xvi, 29; VI, iii, 4; VII, i, 1-2.  For a very good treatment of the influence on Lonergan of Augustine’s early philosophical works, see the chapter by Richard M. Liddy available here.