Empirical Thought Experiments: A Transcendental-Operational View

The operational perspective here defended permits a reflexive-transcendental point of view that sharply distinguishes the two concepts, while, at the same time, maintaining the connection between them. On the one hand, simply imagining that the experimental apparatus, counterfactually anticipated in a thought experiment, has really been constructed is sufficient to erase any difference between thought and real experiments. On the other hand, this very ‘imagining’, this capacity of the mind to assume every real entity as a possible entity, underpins the difference in principle – a properly transcendental difference – between thought and real experiments. This difference, however, implies the intimate association between experiment and thought experiment: All thought experiments must be thought of as translatable into real ones, and all real experiments as realisations of thought ones. What thought experiments have over and above real experiments is the mere fact that they exist in a purely hypothetical sphere; what real have over and above thought experiments is the mere fact that they overstep the sphere of the possible, in the experiment’s real execution. It was noted some time ago by James Brown that a Kantian point of view is lacking in the critical literature on thought experiments (cf. Brown 1991a, p. 156). We now know that this, taken literally, is false. Contrary to what was commonly believed until a few decades ago, it was not Mach who introduced the term ‘thought experiment’, but Hans Christian Örsted; and he did so with the purpose of clarifying an aspect of mathematics and its relation to physical knowledge in Kant. However, this interpretation of the nature of thought experiments and of their relation with real ones has had virtually no impact on the historical development of the concept. This is largely because philosophy of science has mostly taken a course that led to the rejection or dissolution of the Kantian a priori, either in the empiricist direction of Mach, of Neopositivism and of Popper, or in the conventionalist direction of French philosophy, of the relativistic philosophy of science of the 1960s and of the ‘sociological turn’ (that construed the a priori as changeable in function of historically shifting pragmatic interests). It is certainly possible – even though isolated similarities do not quite prove it – that Mach took the term ‘Gedankenexperiment’ from Örsted (cf. Kühne 2005, pp. 186-187). In any case, it is important to keep in mind the differences in principle between their conceptions of thought experiment, in particular as to the acceptance or rejection of the transcendental nature of the a priori. For this reason, the claim that a Kantian point of view is lacking in the critical literature on thought experiments was and is fundamentally correct in its spirit; and it has been my intention to fill this gap. Here, briefly presented, is an account of real and thought experiments in the natural sciences, as it examines their distinction and connection in principle within an operational perspective which brings together the empirical or formal point of view of naturalised epistemologies and the reflexive-transcendental point of view of the Kantian tradition. The account is, in short, at once reflexive-transcendental and operational.