Through an examination of the controversy between Clairaut and Buffon occasioned by Clairaut's proposed revision of Newton's inverse-square law, Clairaut's understanding of Newtonianism is revealed. The interplay in his thought between the possibility of falsification , and the necessity of seeking verification in terms of mathematically precise consequences, indicates a fruitful development of Newtonianism into probabilism. That Clairaut's principles stem from Newton rather than from the Cartesians is indicated by his retention of a delicate balance between the claims of mathematics (...) and those of observation, a balance in which the claims of metaphysics are weightless. (shrink)