Mathematics

Plato, Laws 5.747b (tr. Trevor J. Saunders):

For domestic and public purposes, and all professional skills, no single branch of a child's education has such an enormous range of applications as mathematics; but its greatest advantage is that it wakes up the sleepy ignoramus and makes him quick to understand, retentive and sharp-witted; and thanks to this miraculous science he does better than his natural abilities would have allowed.

πρός τε γὰρ οἰκονομίαν καὶ πρὸς πολιτείαν καὶ πρὸς τὰς τέχνας πάσας ἓν οὐδὲν οὕτω δύναμιν ἔχει παίδειον μάθημα μεγάλην, ὡς ἡ περὶ τοὺς ἀριθμοὺς διατριβή· τὸ δὲ μέγιστον, ὅτι τὸν νυστάζοντα καὶ ἀμαθῆ φύσει ἐγείρει καὶ εὐμαθῆ καὶ μνήμονα καὶ ἀγχίνουν ἀπεργάζεται, παρὰ τὴν αὑτοῦ φύσιν ἐπιδιδόντα θείᾳ τέχνῃ.