1. Laws, Dispositions and Properties A Discussion of Bird's "Nature's Metaphysics" Gerhard Schurz (University of Duesseldorf)

2. I focus on six of Bird's theses: 1) Fundamental properties have dispositional essences. E.g.: Charge + (x) m Disp(Charge (y) n Attract(x,y)) I agree (though I would reduce metaphysical to nomological necessity). 1*) Even 'structural' (geometrical) properties are essentially dispositional. I disagree, because of the ontological regress problem. 2) Hence fundamental properties are not categorial. I would say: not necessarily. They may still be categorial*. 3) Fundamental properties have single-track dispositions as their essence. I disagree: their essences are multi-track dispositions. 4) Laws supervene on properties. I would say: Possibly. But that properties supervene on laws is more plausible (element particle physics). 5) Laws are metaphysically necessary. I agree, if metaphysical necessity is (or supervenes on) physical necessity. 6) We need only one notion of necessity, metaphysical necessity. I disagree: we need to distinguish between analytical and (meta-)physical necessity.

3. On Bird's thesis 1: How can we handle complex properties? 1.1 Only fundamental properties are characterized by essential single-track dispositions. dispositions. 1.2 Not all metaphysically entailed dispositions are essential ones. Common CauseEmpirical Dispositions Common CauseEmpirical Dispositions(Abduction) (Special:) x is soluble in water (Special:)) x is non-soluble in oil (Special:)) x is non-soluble in oil Electric(General:) x is soluble in water-similar Dipole('polar') solvents (ammonia ) Structure(General:) x is not soluble in oil-similar (non-polar) solvents (benzene, ) Structure(General:) x is not soluble in oil-similar (non-polar) solvents (benzene, ) x has an increased melting point x has an increased melting point x-solutions conduct electricity x absorbs electromagnetic radiation in a typical frequency range in a typical frequency range etc. etc. See Schurz, G.: "Patterns of Abduction", Synthese 2007.

4. On Bird's thesis 2: Problems of finks, antidotes (cp's) are handled well. I also agree with Bird that counterfactual possibility must somehow be part of our actual world. Bird argues: Charge is essentially dispositional and hence NOT categorial. But why are "dispositional" and "categorial" disjoint? Because like Armstrong, Bird defines "categorial" as being independent from any dispositions/powers. I agree with Bird's criticism of "quidditism" given a metaphysical understanding of "necessity (independence)". However, Armstrong's notion of "necessity (independence)" is more conceptual (combinatorial) than metaphysical in Bird's sense. Given a (meta-)physical understanding of "necessity", one may also hold: Charge is categorial* in the sense of being metaphysically equivalent with its essential disposition(s), though still categorial in its nature. What is more plausible? Equivalent ways of speaking?

5. On Bird's thesis 3: Mass is essentially characterized by two dispositions: inertial mass and gravitational mass. This does not only hold in Newton's, but in particular in general relativity theory. This does not only hold in Newton's theory, but in particular in general relativity theory. Electric charge has three essential dispositions: 1) electrostatic force which connects it to opposite charges. 2) electrodynamic force which connects it to the magnetic field. 3) dynamic production of waves, which connects it to light. 3) dynamic production of electromagnetic waves, which connects it to light. Conclusion 1: even fundamental properties are have multi-track dispositions as their essences. Conclusion 1: even fundamental properties are have multi-track dispositions as their essences. Conclusion 2: this observation speaks in favour of "categorial*". Conclusion 2: this observation speaks in favour of "categorial*".

6. On Bird's thesis 4: It follows from Bird's view that fundamental properties are metaphysically equivalent with their essential dispositions. Hence it can be said, (fund.) laws supervene on (fund.) properties. But one might also say, (fund.) properties supervene on (fund.) laws. I think it is more adequate to say that (fund.) properties supervene on (fund.) laws, on two reasons: I think it is more adequate to say that (fund.) properties supervene on (fund.) laws, on two reasons: (1) Some properties are non-dispositional (regress-problem). (2) In elementary particle physics, not all elementary properties are characterized by bundles of dispositions of single properties, but merely by conservation laws (system-dispositions) governing particle reactions. Example: the property of strangeness has no special dispositions apart from discriminating between certain types of particles which otherwise would coincide and forbidding certain particle reactions which otherwise were allowed. One might understand conservation laws as being metaphysically entailed by the dispositions of systems of bundles of properties (particles) to entertain certain interactions (particle reactions) under the stimulus of coming close enough to each other.

7. On Bird's thesis 5: Are laws not contingent but metaphysically necessary? Yes, if metaphysical necessity is (or supervenes on) physical necessity. But I fear then the thesis looses its bite.

8. On Bird's thesis 6: Do we need only one notion of necessity: metaphysical necessity? In the history of philosophy "necessity" was a systematically unclear notion. In the history of philosophy "necessity" was a systematically unclear notion. I see only two (three) clear notions of necessity: 1) Analytic necessity: follows from explicit or at least implicit conventions of meaning which govern our concepts. 1*) Logic necessity is a special case of analytic necessity. 2) Physical necessity: follows from fundamental laws of nature. I agree with Bird that Hume's "regularity view of laws of nature" is wrong. Several criteria of lawlikeness which go beyond mere (strict or probabilistic) regularity have been proposed in philosophy of science. Note: Laws of nature which are derivable from fundamental laws of nature and physically contingent boundary conditions do not express physically necessary facts (Galileo's law; biological laws, etc.). Note: Laws of nature which are derivable from fundamental laws of nature and physically contingent boundary conditions do not express physically necessary facts (Galileo's law; biological laws, etc.).

9. On Bird's thesis 6 continued: For purposes of testing laws we need to fix analytic core meanings of properties (so we need analytic necessity/possibility). For example: mass is by semantic con- vention something which can be measured by a pair of scales; let's see what other properties are connected to this 'something' in lawlike manner. For purposes of testing laws we need to fix analytic core meanings of properties (so we need analytic necessity/possibility). For example: mass is by semantic con- vention something which can be measured by a pair of scales; let's see what other properties are connected to this 'something' in lawlike manner. If we would identify mass with all of its dispositions we could not imagine a falsification situation. Hence: thick property conceptions are not useful for theory testing. But they are useful for world-understanding. Different metaphysical positions often rest simply of different notions of necessity: Different metaphysical positions often rest simply of different notions of necessity: Example 1: Bird vs. Armstrong on categorial properties. But Armstrong understands possible worlds more in a conceptual/combinatorial sense. Example 2: Bird's critique of Hume's dictum, that spatiotemporally separated events cannot be necessarily connected. But Hume had logical connection in mind. I do not see a clear notion of metaphysical necessity different from both analytic and physical necessity. I do not see a clear notion of metaphysical necessity different from both analytic and physical necessity. The argument from rigid property designators does not help: even if rigid designation could be achieved by us humans (which I doubt), then rigid designations supervene on the relations among instantiated properties which hold in our world – hence, the metaphysical necessity supervenes on physical necessity.