 In a recent paper (2013), Kripke argues that  CT  may be regarded as a “special corollary” of the completeness theorem for first order logic. Kripke’s argument is reminiscent of one given earlier by Kreisel (1987) concerning, not CT, but rather the relation between informal validity, on the one hand, and formal validity and provability on the other. It is useful to consider Kreisel’s argument first and Kripke’s afterwards (some details of the following are not Kreisel’s):