Medieval Political Philosophy: A Sourcebook. 2nd. Edition. Eds. Joshua Parens and Joseph C. MacFarland. Ithaca: Cornell University Press, 2011. pp. 13-53.
“1. The human things through which nations and citizens of cities attain earthly happiness in this life and supreme happiness in the life beyond are of four kinds: theoretical virtues, deliberative virtues, moral virtues, and practical arts.
2. Theoretical virtues consist in the science whose ultimate purpose is only to make the beings and what they contain intelligible with certainty. This knowledge is in part possessed by man from the outset without his being aware of it and without perceiving how he acquired it or where it comes from. This is primary knowledge. The rest is acquired by meditation, investigation and inference, and instruction and study. The first premises are known by primary knowledge; on their basis one proceeds to the subsequent knowledge gained from investigation, inference, instruction, and study. By investigation or instruction one seeks the knowledge of things that are unknown from the outset: when they are being investigated and their knowledge is sought, they are problems; and afterwards when man by inference or study has been led to conviction, opinion, or knowledge about them become conclusions.
3. The attainment of certain truth is aimed at in every problem. Yet frequently we do not attain certainty. Instead, we may attain certainty about part of what we seek, and belief and persuasion about the rest.”