This paper compares and contrasts relational quantum mechanics with a pragmatist view of quantum theory. I first explain important points of agreement. Then I point to two problems faced by RQM and sketch DP?s solutions to analogous problems. Since both RQM and DP have taken the Born rule to require relative facts I next say what these might be. My main objection to RQM as originally conceived is that its ontology of relative facts is incompatible with scientific objectivity and undercuts (...) the evidential base of quantum theory. In contrast DP?s relative facts have all the objectivity we need to accept quantum theory as scientific knowledge. But a very recent modification to RQM has successfully addressed my main objection,bringing the two views into even closer alignment. (shrink)

I offer an account of how the quantum theory we have helps us explain the enormous variety of phenomena it is generally taken to explain. The account depends on what I have elsewhere called a pragmatist interpretation of the theory. This rejects views according to which a quantum state describes or represents a physical system, holding instead that it functions as a source of sound advice to physically situated agents like us on the content and appropriate degree of belief about (...) matters concerning which they are currently inevitably ignorant. So while the account given here is incompatible with some views of structural explanation in quantum theory it is nevertheless able to incorporate what I take to be their valuable insights. (shrink)

In his recent work, Michael Redhead (1986, 1987, 1989, 1990) has introduced a condition he calls robustness which, he argues, a relation must satisfy in order to be causal. He has used this condition to argue further that EPR-type correlations are neither the result of a direct causal connection between the correlated events, nor the result of a common cause associated with the source of the particle pairs which feature in these events. Andrew Elby (1992) has used this same condition (...) as a premise in an independent argument for the conclusion that EPR-type correlations cannot be causally explained (except, perhaps, by a nonlocal hidden variable theory). I wish to argue here that robustness is itself too fragile a notion to support such conclusions. (shrink)

In papers published in the 25 years following his famous 1964 proof John Bell refined and reformulated his views on locality and causality. Although his formulations of local causality were in terms of probability, he had little to say about that notion. But assumptions about probability are implicit in his arguments and conclusions. Probability does not conform to these assumptions when quantum mechanics is applied to account for the particular correlations Bell argues are locally inexplicable. This account involves no superluminal (...) action and there is even a sense in which it is local, but it is in tension with the requirement that the direct causes and effects of events are nearby. (shrink)

Bell appealed to the theory of relativity in formulating his principle of local causality. But he maintained that quantum field theories do not conform to that principle, even when their field equations are relativistically covariant and their observable algebras satisfy a relativistically motivated microcausality condition. A pragmatist view of quantum theory and an interventionist approach to causation prompt the reevaluation of local causality and microcausality. Local causality cannot be understood as a reasonable requirement on relativistic quantum field theories: it is (...) unmotivated even if applicable to them. But microcausality emerges as a sufficient condition for the consistent application of a relativistic quantum field theory. (shrink)

The status of laws of nature has been the locus of a lively debate in recent philosophy. Most participants have assumed laws play an important role in science and metaphysics while seeking their objective ground in the natural world, though some skeptics have questioned this assumption. So-called Humeans look to base laws on actual, particular facts such as those specified in David Lewis’s Humean mosaic. Their opponents argue that such a basis is neither necessary nor sufficient to support the independent (...) existence of scientific laws. This essentially metaphysical debate has paid scant attention to the details of scientific practice. It has mostly focused on so-called fundamental laws, assumed to take a particular form. I propose a pragmatist alternative—not as another position in the debate but as an alternative to the debate itself. This pragmatist alternative offers a view that questions the representational conception of truth presupposed by participants to the debate as well as the metaphysical import of fundamental laws. Statements of law serve many different purposes in science: I’ll look at some. But their central role is in inference, primarily to improve the epistemic state of a scientist with limited access to information. To play this role, a scientific law statement need be neither necessary, unconditionally universal nor even true. It must merely be sufficiently reliable within its domain of application. The use of laws in astrophysics and metrology will help to illustrate these points. (shrink)

A quantum state represents neither properties of a physical system nor anyone's knowledge of its properties. The important question is not what quantum states represent but how they are used as informational bridges. Knowing about some physical situations, an agent may assign a quantum state to form expectations about other possible physical situations. Quantum states are objective: only expectations based on correct state assignments are generally reliable. If a quantum state represents anything, it is the objective probabilistic relations between its (...) backing conditions and its advice conditions. This paper offers an account of quantum states and their function as informational bridges, in quantum teleportation and elsewhere. (shrink)