In Where the Conflict Really Lies, which James Beebe has nicely reviewed, Alvin Plantinga discusses nomological necessity, the necessity had by physical laws. As he (and everybody else) points out, propositions like
2) Every sphere made of gold is less than 1/2 mile in diameter
are true and universal. However, there is a clear sense in which (2) is not necessary in the sense required for lawhood (the sort of necessity we call ‘nomological necessity’). On the other hand, the proposition that no object can increase from a velocity less than the speed of light to a velocity more than the speed of light is nomologically necessary. Also, it does not seem that this proposition is necessary in the broadly logical or metaphysical sense; the law seems contingent.
How are we to understand nomological necessity? Plantinga suggests:
The sense in which the laws of nature are necessary, therefore, is that they are propositions God has established or decreed, and no creature–no finite power, we might say–has the power to act against these propositions, that is, to bring it about that they are false (281).
(Moon’s comment: the second conjunct here seems to be entailed by the first; if God has “established or decreed the proposition”, then no finite power can make it false. So, the second conjunct is technically redundant, but I think it is still informative.) Plantinga goes on to illustrate,
It is as if God says: “Let c, the speed of light, be such that no material object accelerates from a velocity less than c to a velocity greater than c”; no creaturely power is then able to cause a material object to accelerate from a velocity less than c to one greater than c. The laws of nature, therefore, resemble necessary truths in that there is nothing we or other creatures can do to render them false… Though these laws are finitely violable, they are nevertheless contingent, in that it is not necessary, not part of the divine nature, to institute or promulgate just these laws. God could have created the world in such a way that the speed of light should have something quite different from c (281)
Plantinga later writes, while summing up the section,
Third, theism enables us to understand the necessity or inevitableness or inviolability of natural law: this necessity is to be explained and understood in terms of the difference between divine power and the power of finite creature. Again, from the point of view of naturalism, the character of these laws is something of an enigma. What is this alleged necessity that they display, weaker than logical necessity, but necessity nonetheless? (283)
Two questions. First, can anybody think of any problems with Plantinga’s theistic account? Second, I wonder if naturalists do have alternative accounts of nomological necessity. Plantinga does mention/cite how some naturalists have reduced nomological necessity to metaphysical necessity; I wonder if there are naturalists who don’t take this route. This is outside of my area, so I’m curious what other people know.