 Since Poincaré so profoundly modifies the traditional view of geometry as the a priori science of space, authors such as Schlick, Carnap, and Ernest Nagel (1939, 1979) attribute to him a leading role in the development of the formal conception of mathematics. Alberto Coffa extends Nagel’s analysis by claiming that there was a crisis in the interpretation of primitive geometrical terms in the nineteenth century that led to the development of formal axiomatic systems (Coffa 1986). References to a central role played by Poincaré can also be found in Joan Richards’ survey (Richards 1994) and in Jeremy Gray’s account of the development of modernism (Gray 2008). The modernist character of Poincaré’s approach is also shown by the fact that he must be ranked with Duhem among those forerunners of logical empiricism who survive Quine’s criticism of the movement, not primarily for his holistic thesis concerning theory-confirmation, more so for his conception of geometrical conventions as a kind of hybrid analytic-synthetic expressions “guided” by experience and for his ontological “relationalism” which in certain aspects comes close to Quine’s doctrine. Both attempt to account philosophically for the incompleteness of (scientific) objects.