The scientific ethos of the modern Western world contains two conflicting moods, of utter lack of assurance and of utter assurance. The question posed here is, how do the two go together? The answer I offer is, all assurance is contingent on the supposition that our system as a whole, still survives, but there is no assurance for the survival of the system as a whole.The mood of agnosticism, expressed in the music of Schoenberg and Webem (even though the latter, at least, was profoundly religious), in the art of Jackson Pollack and Franz Kline, in Buñuel’s ‘Los Olvidados’, and in ever so many other manifestations of the modern world, is philosophically best expressed in Bertrand Russell's ‘Free Man’s Worship’.