[Not enough is known about solid geometry] and for two reasons: in the first place, no government places value on it; this leads to a lack of energy in the pursuit of it, and it is difficult. In the second place, students cannot learn it unless they have a teacher. But then a teacher can hardly be found.
PlatoHarmony is a symphony, and symphony is an agreement; but an agreement of disagreements while they disagree there cannot be; you cannot harmonize that which disagrees.
Plato