Didascalicon, Book I (chapters 2-13): the origin of the arts and the division of philosophy
Chapter XIII. Epilogue of the foregoing
It is fitting, then, to recapitulate briefly what has been said above, that the passage to what follows may be easier. We have said that there are only four sciences which contain all the rest: the theoretical, which labors in the contemplation of truth; the practical, which considers the discipline of morals; the mechanical, which dispenses the actions of this life; and logic, which furnishes the science of speaking rightly and disputing acutely. Here, then, that fourfold number of the soul may not absurdly be understood, which the ancients, out of reverence for it, had taken into their oath. Hence also it was said:
By him who gave to our mind the number four.
How these are contained under philosophy, and in turn what they contain under themselves, let us show by briefly repeating the definition of the philosophers.