Measurement and the interpretation of quantum mechanics and relativity theory

The axiomatic approaches of quantum mechanics and relativity theory are compared with approaches in which the theories are thought to describe readings of certain measurement operations. The usual axioms are shown to correspond with classes of ideal measurements. The necessity is discussed of generalizing the formalisms of both quantum mechanics and relativity theory so as to encompass more realistic nonideal measurements. It is argued that this generalization favours an empiricist interpretation of the mathematical formalisms over a realist one.     

Carnap and weyl on the foundations of geometry and relativity theory

An earlier version of this paper was presented at a workshop on Semantical Aspects of Space-Time Theories at the Zentrum für interdisziplinäre Forschung at the Universität Bielefeld in May 1994. I am indebted to the participants for helpful comments. I am also, and especially, indebted to comments from and discussions with Thomas Ryckman. All translations from the German are my own.     

Causality in medicine: Towards a theory and terminology

One of the cornerstones of modern medicine is the search for what causes diseases to develop. A conception of multifactorial disease causes has emerged over the years. Theories of disease causation, however, have not quite been developed in accordance with this view. It is the purpose of this paper to provide a fundamental explication of aspects of causation relevant for discussing causes of disease. The first part of the analysis will discuss discrimination between singular and general causality. Singular causality, as in the specific patient, is a relation between a concrete sequence of causally linked events. General causation, e.g. as in disease etiology, means various categories of causal relations between event types. The paper introduces the concept of a reference case serving as a source for causal inference, reaching beyond the concept of general causality. The second part of the analysis provides exemplification of a theory of causation suitable for discussing singular causation. The chain of events that induce a disease state can be identified as effective causal complexes, each complex composed of nonredundant components, which separately contribute to the effect of the complex, without the individual component being necessary or sufficient in itself to produce the effect. In the third part of the analysis the theory is elaborated further. Causes, defined as nonredundant components, can furthermore be differentiated according to their avoidability, according to theories about human error or by the potential of eradication. Multifactorial models of disease creates a need for systematic approaches to causal factors. The paper proposes a taxonomical terminology that serves this purpose.     

Ego analysis and the relativity of defense: technical implications of the structural theory

We suggest that it is recognition of the relativity of defense, of the fact that the same content can be either defense or wish, rather than recognition of unconscious defense, that distinguishes the structural from the topographic theory. The structural theory did not simply add to the topographic theory the recognition that defense can be unconscious; it represents a radical shift in the concept of defense and of the relation between defense and wish. Accordingly, ego analysis, as the technical approach generated by the structural theory, is not complementary or preliminary to id analysis, the technical approach generated by the topographic theory. We attempt to demonstrate that the two theories represent antagonistic paradigms, both theoretically and technically. We suggest that "defense before drive," the structural formula for interpretation, made ego syntonicity a crucial determinant in formulating interpretations, and assumed the relativity of defense. Accordingly, the structural revision made possible an equidistant position between defense and wish, reducing reliance on suggestion and establishing interpretive neutrality, which we distinguish from behavioral neutrality.     

Complementarity meets general relativity: A study in ontological commitments and theory unification

The apparent underdetermination of the formalism of quantum field theory (QFT) as between a particle and a field interpretation is studied in this paper through a detour over the problem of unifying QFT with general relativity. All we have at present is a partial or approximate unification, QFT in non-Minkowskian spaces. The nature of this hybrid and the problem of its internal consistency are discussed. One of its most striking implications is that particles do not have an observer-independent existence. We trace the ways in which physicists reacted to this at first highly implausible ontological consequence. We conclude that quantum fields rather than particles are after all the basic entities in QFT.I should like to thank Professors Jürgen Audretsch, Paul Teller and Dr. Martin Carrier for helpful comments.     

Causality and the perception of time

Does our perception of when an event occurs depend on whether we caused it? A recent study suggests that when we perceive our actions to cause an event, it seems to occur earlier than if we did not cause it.     

A theory of causality: Causality=interaction (as defined by a suitable quantum field theory)

In this paper I put forward a suggestion for identifying causality in micro-systems with the specific quantum field theoretic interactions that occur in such systems. I first argue — along the lines of general transference theories — that such a physicalistic account is essential to an understanding of causation; I then proceed to sketch the concept of interaction as it occurs in quantum field theory and I do so from both a formal and an informal point of view. Finally, I present reasons for thinking that only a quantum field theoretic account can do the job — in particular I rely on a theorem by D. Currie and to the effect that interaction cannot be described in (a Hamiltonian formulation of) Classical Mechanics. Throughout the paper I attempt to suggest that the widespread scepticism about the ability of quantum theory to support a theory of causality is mistaken and rests on several misunderstandings.