 Several other authors formulated similar definitions, such as Billingham (Weber 2003, 80) and Fland (Fland/Spade 1976). Normore (1993, 449) argues that a significant transformation occurred in the 14th century British tradition, which “puts in play the idea that deduction is not an objective relation between abstract objects or sentences but a mental operation performed on the bases of what can be understood or imagined.” This is noticeable not only in the definitions of formal (as opposed to material) consequence, but also in the very definitions of consequence which begin to mention mental acts, such as: “a consequence is a derivation (illatio) of the consequent from the antecedent” (Strode, quoted in Normore 1993, 449).