XXIX.

For what is useful and necessary to salvation, such as the knowledge of the Father, and Son, and Holy Spirit, and also of our own soul, are wholly requisite; and it is at once beneficial and necessary to attain to the scientific account of them. And to those who have assumed the lead in doing good, much experience is advantageous; so that none of the things which appear to be known necessarily and eruditely by others may escape their notice. The exposition, too, of heterodox teaching affords another exercise of the inquiring soul, and keeps the disciple from being seduced from the truth, by his having already had practice beforehand in sounding all round on warlike instruments of music. ¹