Summary |
If it is a law that p then p must happen, or, the converse, if a law forbids p then p cannot happen. Yet, what about the laws themselves? Must they be as they are, or could they have been different? Many Humeans (Lewis and most other proponents of the Best System Analysis) and Non-Humeans alike (Dretske, Tooley, Armstrong, Mumford, Maudlin, etc.) do not think that the laws themselves are metaphysically necessary. However, for some dispositional essentialists (Bird, Ellis) who trace back the source of necessity to fundamental essential dispositional properties the metaphysical necessity of laws is a corollary. A. Wilson proposes a Humean version of the metaphysical necessity of laws, and Marc Lange defended the claim that the fundamental subjunctive facts which (on his account) ground the laws explain their purported necessity (see the section on stability theory). Now, whether the laws themselves are (metaphysically) necessary or not, they still confer some kind of necessity to their instances. To repeat, if it is a law that p then p must happen, i.e. p happens with nomological necessity. Different accounts of laws of nature count for this necessity in different ways: Lewis by a kind of stipulation; Armstrong, Tooley and Dretske partially by their necessitation universal (incurring van Fraassen’s the infamous inference problem); and dispositionalists, by the dispositional powers of natural properties. For those who believe the laws themselves are necessary the necessity of their instances comes mostly for free. Related to the subject of the laws’ necessity, theorists differ how (if at all) to spell out the idea that laws govern or constrain or necessitate their instances. |