Response to critical comments by Edward Slowik on my article 'Leibniz on Motion and the Equivalence of Hypotheses' in The Leibniz Review 18 (2008).

The paper investigates possible readings of the later Heisenberg's remarks on the nature of quantum states. It discusses, in particular, whether Heisenberg should be seen as a proponent of the epistemic conception of states – the view that quantum states are not descriptions of quantum systems but rather reflect the state assigning observers' epistemic relations to these systems. On the one hand, it seems plausible that Heisenberg subscribes to that view, given how he defends the notorious "collapse of the wave (...) function" by relating it to a sudden change in the epistemic situation of the observer registering a measured result. On the other hand, his remarks on quantum probabilities as "potentia" or "objective tendencies" are difficult to reconcile with such a reading. The accounts that are attributed to Heisenberg by the different possible readings considered are subjected to closer scrutiny; at the same time, their respective virtues and problems are discussed. _German_ Diese Arbeit untersucht mögliche Lesarten von Heisenbergs späten Bemerkungen über die Natur von Quantenzuständen. Insbesondere wird die Frage diskutiert, ob Heisenberg als Vertreter der epistemischen Auffassung von Quantenzuständen gelten kann – der Idee, dass Quantenzustände nicht Beschreibungen der objektiven Eigenschaften von Quantensystemen sind sondern die epistemischen Beziehungen von Beobachtern zu diesen Systemen widerspiegeln. Einerseits erscheint es plausibel, dass Heisenberg dieser Sichtweise zustimmt, wenn man sich ansieht, wie er den berüchtigten,,Kollaps der Wellenfunktion" verteidigt, indem er ihn mit einer plötzlichen Änderung in der Kenntnis des ein Messergebnis registrierenden Beobachters in Zusammenhang bringt. Andererseits sind seine Bemerkungen über quantenmechanische Wahrscheinlichkeiten als,,Potentia" oder,,objektive Tendenzen" mit einer solchen Lesart nur schwer in Einklang zu bringen. Die Positionen, die Heisenberg den verschiedenen möglichen Lesarten zufolge vertritt, werden eingehenden Untersuchungen unterzogen; gleichzeitig werden ihre jeweiligen Vorzüge und Probleme diskutiert. (shrink)

In the present paper we study the relationship between the notions of force, cause and subject of motion in Leibniz’s early dynamics. First, we specify the role that the problem of the subject and cause of motion played in the development of his dynamics. Second, we analyze the distinction between force and quantity of motion and the validity and limits of his proof. Third, we study and evaluate the limits of the arguments for establishing that forces are inherent to bodies. (...) Our main goal is to show that between 1678 and 1686 Leibniz dissociates the problem of the subject from the problem of the cause of motion and, furthermore, that even though the problem of establishing that force is inherent to particular bodies played a major role in the discovery of his dynamics, it has no place in its justification. (shrink)

In the texts of the middle years (roughly, the 1680s and 90s), Leibniz appears to endorse two incompatible approaches to motion, one a realist approach, the other a phenomenalist approach. I argue that once we attend to certain nuances in his account we can see that in fact he has only one, coherent approach to motion during this period. I conclude by considering whether the view of motion I want to impute to Leibniz during his middle years ranks as a (...) kind of realism or rather as some kind of phenomenalism or idealism. (shrink)

Spending six months in Rome in 1689 Gottfried Wilhelm Leibniz (1646–1716) occupied himself with the question of Copernican and Galilean censure. An established reading of the Rome papers suggests that Leibniz’s attempt to have the Copernican censure lifted was derived solely from the equivalence of hypotheses stemming from the relativity of motion; and involved Leibniz’s compromising his belief in the truth of the Copernican hypothesis by arguing that it should only be interpreted instrumentally; and that Leibniz believed in the unrestricted (...) abolition of censure. On the contrary, I argue that if hypotheses were merely equivalent, this would not provide a reason for lifting censure of Galileo, who argued that the Earth really moves and the Church was in error on this point; that Leibniz’s position in his cosmology was indeed a kind of instrumentalism, so that it did not involve any compromise; and that Leibniz is advocating a position that Galileo should be subject to censure, not because of his physics but rather because of his misinterpretation of the status of Scripture. (shrink)

Einstein’s “point-coincidence argument'” as a response to the “hole argument” is usually considered as an expression of “Leibniz equivalence,” a restatement of indiscernibility in the sense of Leibniz. Through a historical-critical analysis of Logical Empiricists' interpretation of General Relativity, the paper attempts to show that this labeling is misleading. Logical Empiricists tried explicitly to understand the point-coincidence argument as an indiscernibility argument of the Leibnizian kind, such as those formulated in the 19th century debate about geometry, by authors such as (...) Poincaré, Helmholtz or Hausdorff. However, they clearly failed to give a plausible account of General Relativity. Thus the point-coincidence/hole argument cannot be interpreted as Leibnizian indiscernibility argument, but must be considered as an indiscernibility argument of a new kind. Weyl's analysis of Leibniz's and Einstein's indiscernibility arguments is used to support this claim. (shrink)