This paper addresses Peter Sloterdijk’s optimistic ‘attitude’. I show that it is a philosophical posture based on pragmatic speculation and spiritual exercise. By situating it in a tradition that passes from Leibniz’s meliorism to Whitehead’s ecology of propositions, I argue that optimism is an essential component of a public use of reason of which the finality is no longer the good sense of critique but of the care for common sense. At stake is the cosmological and cosmopolitical care for the (...) possibility of rationalization processes in a ‘monstruous world’ of ever denser feedback mechanisms. (shrink)