 However surprising it may initially seem, contemporary developments in the philosophy of science can only be properly appreciated in relation to the historical background of logical positivism. Hempel himself attained a certain degree of prominence as a critic of this movement. Language, Truth and Logic (1936; 2nd edition, 1946), authored by A.J. Ayer, offers a lucid exposition of the movement, which was—with certain variations—based upon the analytic/synthetic distinction, the observational/theoretical distinction, and the verifiability criterion of meaningfulness. A fundamental desideratum motivating its members was to establish standards for separating genuine questions for which answers might be found from pseudo-questions for which no answers could be found.