What use does the jurist have for rules and principles? What relation does he or she have to the articulation of facts? This paper considers the position of facts and rules in the casuistry of the Roman jurists. Two textual analyses of the Digest of Justinian are presented: a reading of Digest 9.2.27.12 (a statement by Ulpian on the application of the lex Aquilia to the situation of the burning of some bees) and Digest 45.3.18.2 (a consideration by Papinian of a difficult case concerning the fate of a contract made by a slave while his owner was in captivity). The paper argues that these fragments reveal the craft of the jurist in unexpected ways. What at first appears as the awkwardness of expression in them turns out to disclose a remarkable lucidity. Framed through a reading of the work of Yan Thomas, these fragments provide two nodal points for unveiling the nature of an art that does not ask what law is but seeks to isolate it in its cases.