Abstract

On Einstein’s Imaginary Dialogue between

Poincare, Reichenbach and himself

Samet Bagce, METU, Department of Philosophy

Einstein had a deep respect for Reichenbach’s work on space, time and relativity. In Albert Einstein: Philosopher-Scientist [Schilpp (1949), pp.287-312]. Reichenbach states some of the central theses of his 1928 book, The Philosophy of Space and Time. In his reply Einstein brings in an imaginary dialogue between Poincare and Reichenbach [pp.677-679]. After the dialogue, Einstein remarks: “I can hardly think of anything more stimulating as the basis for discussion in an epistemological seminar than this brief essay by Reichenbach” [p.679].

The dialogue is initiated by the desire of finding the correct answer for the following question: “Is a geometry –looked from the physical point of view- verifiable (viz., falsifiable) or not?” Einstein goes on to say that “Reichenbach, together with Helmholtz, says: Yes, provided that the empirically given solid body realizes the concept of “distance”. Poincare says not, and consequently is condemned by Reichenbach” [pp.676-677]. Einstein then brings in the dialogue, which takes place between Poincare and Reichenbach. However, the aim of his dialogue seems to support Reichenbach’s position. This is so because Einstein at a certain point halts the dialogue by saying that “the respect of the [present] writer for Poincare”s superiority as thinker and author does not permit” the dialogue to go on in that fashion. That is a very tactful way of saying that Einstein sides with Reichenbach on this issue and Einstein’s “respect for Poincare” does allow him to maintain that Poincare is at fault here. So an anonymous non-positivist is substituted for Poincare in the rest of the dialogue. Actually, the dialogue is then between three people, Poincare, Reichenbach and Einstein himself.

In this talk my aim is to carry on this imaginary dialogue in order to argue for the following claims so that the injustice done to Poincare shall be removed:

(a)    Reichenbach misunderstands Poincare’s position: Poincare himself never used the appellation “conventionalism” either for his general philosophy or for his account of geometry. Moreover, Poincare never adhered to a distinction between physical and pure geometry; on the contrary, he was totally against it.

(b)    Reichenbach’s position can be criticized from several perspectives:

(i)     the formulation of non-customary congruence definitions in terms of deformations by universal forces has been regarded as ad hoc [cf. Nagel (1982), p.264].

(ii)    the conflational use of universal forces both in literal and metaphorical senses renders the definition of rigidity as paradoxical.

(iii)  Reichenbach’s thesis of relativity of geometry implies that “if we change the coordinative definition of congruence, a different geometry will result”. However, this is not the case [cf. Grunbaum (1973), pp.98-105).

(iv)  Reichenbach’s proposed outline of a characterization of synonymy yielded in some technical difficulties, i.e., it undermines the viability of any proof theory.

(v)   In gaining the real definition of the intervals one has to make use of physical laws. So, the empirical confirmation/falsification here refers not merely to geometry but to the entire system of physical laws which constitute its very foundation. Thus, the distinction between pure and physical geometry is untenable.