David Chalmers

A familiar interpretation of quantum mechanics (one of a number of views sometimes labeled the "Copenhagen interpretation'"), takes its empirical apparatus at face value, holding that the quantum wave function evolves by the Schrödinger equation except on certain occasions of measurement, when it collapses into a new state according to the Born rule. This interpretation is widely rejected, primarily because it faces the measurement problem: "measurement" is too imprecise for use in a fundamental physical theory. We argue that this is a weak objection, as there may be many ways of making "measurement" precise. However, measurement-collapse interpretations face a more serious objection: a dilemma tied to the quantum Zeno effect. Is measurement itself an observable that can enter superpositions? If yes, then the standard measurement-collapse dynamics is ill-defined. If no, then (at least if measurement is an observable), measurements can never start or finish. The best way out is to deny that measurement is an observable, but this leads to strong and revisionary consequences. This reinforces the view that there is no nonrevisionary interpretation of quantum mechanics.

Does consciousness collapse the quantum wave function? This idea was taken seriously by John von Neumann and Eugene Wigner but is now widely dismissed. We develop the idea by combining a mathematical theory of consciousness (integrated information theory) with an account of quantum collapse dynamics (continuous spontaneous localization). Simple versions of the theory are falsified by the quantum Zeno effect, but more complex versions remain compatible with empirical evidence. In principle, versions of the theory can be tested by experiments with quantum computers. The upshot is not that consciousness-collapse interpretations are clearly correct, but that there is a research program here worth exploring.

This chapter explores the conceptual landscape of the most important, current critique of panpsychism—the combination problem. He sets out from the ‘locus classicus’: William James’s presentation of the combination problem in his 1890 _The Principles of Psychology_. He discerns three ways of formulating the problem, which evolve around three distinct characteristics of phenomenal states: the subject combination problem, the quality combination problem, and the structural combination problem. Chalmers then turns to seven subversions of these three versions. The first four are connected to the subject combination problem. Subversion five and six are connected to the quality combination problem. And the final explication is connected to the structural combination problem. The chapter closes by presenting various solutions and answers to these explications of the combination problem.

I reply to seven commentaries on “The Virtual and the Real”. In response to Claus Beisbart, Jesper Juul, Peter Ludlow, and Neil McDonnell and Nathan Wildman, I clarify and develop my view that virtual are digital objects, with special attention to the nature of digital objects and data structures. In response to Alyssa Ney and Eric Schwitzgebel, I clarify and defend my spatial functionalism, with special attention to the connections between space and consciousness. In response to Marc Silcox, I clarify and develop my view of the value of virtual worlds, with special attention to the case where we experience these worlds as virtual.

Is there progress in philosophy? A What might be called a glass-half-full view of philosophical progress is that there is some progress in philosophy. The glass-half-empty view is that there is not as much as we would like. Inspired in part by van Inwagen’s discussion of disagreement in philosophy, this paper articulates and argues for a thesis about the relative lack of progress in philosophy: there has been less convergence to the truth on the big questions of philosophy than on the big questions of the hard sciences. It then investigates the question of what explains this relative lack of progress. The paper considers a number of explanations and argues that none of them is fully adequate. It then articulates a form that an adequate explanation might take.

I present an argument for panpsychism: the thesis that everything is conscious, or at least that fundamental physical entities are conscious. The argument takes a Hegelian dialectical form. Panpsychism emerges as a synthesis of the thesis of materalism and the antithesis of dualism. In particular, the key premises of the causal argument for materialism and the conceivability argument for dualism are all accommodated by a certain version of panpsychism. This synthesis has its own antithesis in turn: panprotopsychism, the thesis that fundamental physical entities are protoconscious, also accommodates the key premises. Panpsychism and panprotopsychism are synthesized under Russellian monism, and then face an antithesis, the combination problem. The question of whether there is a new synthesis remains open.