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metaphysics of science

an AHRC funded research project

doctoral research

The Project supports two PhD studentships, one each at the Universities of Birmingham and Nottingham.

The topics of the studentships are:

Natural Kinds (Birmingham)

PhD project description

The broad topic that Nigel is investigating is 'Natural Kinds' as it appears both in post-Kripkean philosophy of language and in recent work in the philosophy of science and the metaphysics of laws. His research also feeds into the broader project, with its overarching focus on the metaphysics of laws, dispositions and causation.

Role within project

The notion of a natural kind plays a key role in many of the issues that are central to the project as a whole. One very important, but neglected, question concerns whether, or to what extent, the notion of a natural kind as it appears in the post-Kripkean philosophy of language literature is the same notion as the notion of a natural kind appealed to in recent work on the metaphysics of laws.

On the philosophy of language side, the dominant view is that some general terms (water, tiger, gold, etc.) pick out natural kinds in the sense that reference across possible worlds goes along with some underlying essence rather than with manifest properties, the justification for this claim resting on our ordinary intuitions about Twin Earth-type thought experiments. However, the notion of a natural kind as it often appears in work on the metaphysics of laws (for example in Brian Ellis's Scientific Essentialism) stems from a very different origin: the desire to find a classificatory system which 'carves nature at its joints' and which also thereby places constraints on what sorts of entities can be the subject-matter of laws of nature.

There are at least prima facie tensions between these two approaches. For example, Ellis argues that there are no natural biological kinds, while Kripkean intuitions seem to support the view that there are such kinds. Another example: for Ellis, the 'essences' of the most basic natural kinds are at least sometimes dispositional. But broadly Kripkean intuitions seem to rule this possibility out; for example, mental states like beliefs and desires, on a functionalist account, cannot constitute natural kinds precisely because they are defined in terms of their typical causes and effects, and not in terms of their underlying (categorical) nature. The viability of the essentialist programme pursued by Ellis and others depends upon its deploying a viable notion of a natural kind; this issue therefore requires further investigation.

Relatedly, the notion of a 'natural' kind or a 'natural' property plays a central role in some contemporary discussions of mental and special science causation. Classification in terms of mental properties cross-cuts classification in terms of underlying physical properties (unless a type-identity theory is true), and it is often taken for granted that mental properties therefore cannot play a role in genuine laws of nature, and so cannot be genuinely causally efficacious. The issue of precisely why the laws of nature must all be located at the same, rock-bottom level (physics) if some form of physicalism is true, and the corresponding question of why mental kinds are 'unnatural', requires further investigation if a satisfactory solution to the problem of mental causation is to be found.

Powers and Causation (Nottingham)

PhD project description

The broad topic that Matt is investigating is "Powers and Causation". A number of philosophers have claimed in recent years that an ontology of causal powers can deliver a theory of causation, such as Harré, Bhaskar, Cartwright, Ellis and Molnar. Matt is investigating this topic as it appears in recent work in the philosophy of science and metaphysics. Matt will ultimately question whether a plausible theory of causation can be gained from a powers ontology.

Role within project

The nature and importance of causal powers has been a continuing theme of the metaphysics in science group, mainly through the work of Mumford and Bird but also because of the high level of constructive criticism that has been received from the group's more Humean members.

A dispositional ontology, admitting a category of power or capacity, is thought by some to offer a vital insight into the nature of causation. Proponents of this view believe that other ontologies do not have the metaphysical resources to capture this insight. At its most ambitious, a causal powers ontology purports to offer a solution to, or dissolution of, the problem of causation. The argument is that the traditional problem of causation is generated by a faulty Humean ontology in which the world is described as a sum of 'loose and separate' distinct existences (Hume 1748: 74). Once the main Humean premise, of there being no necessary connections between distinct existences, is accepted then the notion of causation becomes immediately problematic. This most common sense and widely accepted of notions, which is arguably a part of everyone's pre-critical understanding of the world, is then either rejected outright or its defenders are forced to fight a rearguard action, presenting ever more elaborate theories to underwrite something so simple and basic.

The dispositionalist programme is still in its relative infancy and it needs to be shown in detail how the theory accounts for causation. In most cases, it has been assumed that a theory of causation falls unproblematically from the theory of powers but it is not immediately obvious how it does so (and just calling them causal powers is no substitute for such an account). In addition to this, opponents ask what reason we have to believe in such things as causal powers in the first place. Dispositionalists do not rise to the Humean sceptical challenge about necessary connections in nature. They tend either to ignore it or say that it is not worth answering. There is, nevertheless, optimism among dispositionalists that both these problems can be answered. In the first place, an account of how to get causes from powers was started by Molnar (2003: ch. 12) and this account may yet come to be the foundation of a robust dispositionalist theory of causation. In the second place, dispositionalists regard Hume's challenge as a form of scepticism that cannot be tackled on its own terms. The powers ontology rejects the whole apparatus that raises causation as a problem. The argument for accepting powers is in their overall productivity compared to Humean alternatives. Like other theories in metaphysics, this one is to be accepted because, its supporters argue, it accounts for troublesome phenomena in a plausible and economical way. If one accepts powers as the basic ontological category, one can produce plausible theories of properties, laws of nature, modality and causation. The success of producing a theory of causation is, therefore, one of the reasons for accepting the powers ontology in the first place.