Marsilio Ficino’s Platonic Theology, Volume II

19Body is long, broad, and deep. Yet because no body is infinite and it therefore has a limit to its depth, it is bounded by a surface without depth. You now have a surface, long and broad like a body, but lacking depth and in this one respect rising toward incorporeal things. The breadth of the surface, being finite, likewise ends at a long line which is neither deep nor broad. You have a line approaching spirit in two respects. Yet because the length of the line is itself finite, it is brought to a point deprived not only of depth and breadth, but also of length. You have a point inclining in three respects toward incorporeal nature. But because it is the limit of a line, it has a determinate position in the body and neither fills the whole nor gives it life. Separate it, if you please, from the line. It can at least in thought be separated from the line, because it is the line's limit and in a certain way exists in itself before it bounds the line. What is prior may be separated from what is posterior. You now have a point in some manner—that is, in thought—released from the line and withdrawing from body by a fourth degree. In this very release, let it attain the power to regard all parts of the body equally. Let it be diffused throughout them all and move them. Here the irrational soul has its seat.

20And because rational thought is not deceived in its ascent, just as it discovered a point freed from body in thought, so in reality it will discover a point—that is, an indivisible something actually released from body. This not only fills and moves the body, but is itself freely moved and raised to things above; and it is now called by the name of unity. Here the rational soul thrives, removed from the bulk of body by a fifth degree. If a thing is more impure the more it needs and undergoes, body is more impure than surface. In order to exist, it needs more dimensions and is divided into more parts. For the same reason surface yields to line, line to point, and point at last to unity, which needs neither dimensions nor position. If substantial unity is the most perfect of these, and because it is most perfect is therefore the most powerful and the most true, and if these other things are something and do exist, who will deny that unity truly exists? What, then, prevents the soul from being something, and indeed something great in power, although it is not something great in quantity?