Laws, natural

It is widely supposed that science aims to identify ’natural laws’. But what are laws of nature? How, if at all, do statements of laws differ from ’mere’ general truths which include generalizations true only ’accidentally’? Suppose, for example, it happens to be true that all iron spheres (past, present and future) are less than 1 km in diameter. Contrast this with the truth of ’all electrons are negatively charged’. There seems to be a clear intuitive distinction between these two truths, but is there any principled distinction between them that can be drawn and defended? This has been the traditional focus of philosophical attention concerning laws of nature, and basically two mutually opposed philosophical accounts have been developed. According to the first account, there are real necessities in nature, over and above the regularities that they allegedly produce (whether or not these regularities are held to be observable), and law-statements are descriptions of these necessities. According to the second account, there are no necessities but only regularities (correlations, patterns) and laws are descriptions of regularities (though perhaps not of any regularity but only of the most basic or most general ones). There are significantly different variants of each account; and also positions that altogether deny the existence of general laws (or deny that science should aim to describe them). Any one of these accounts, if it is ultimately to be coherent and defensible, has to successfully address four interrelated issues: the meaning of a law statement – the semantic issue; the fact to which a law statement refers and which makes it true – the metaphysical issue; the basis on which claims to know a law are justified – the epistemological issue; the capacity to explain adequately the variety and roles of scientific laws – the explanatory issue. In attempting this task, each of the available accounts faces its own distinct difficulties. For example, if there are necessities in nature, as the first account claims, how exactly do we identify them: how can we tell which of the inductively confirmed regularities are laws? On the other hand, if there are only regularities, as the second account claims, does this mean that our intuitions and scientific practices are awry and that there really is no distinction between laws and accidental generalizations? The difficulties facing all extant accounts become even more marked when we face up squarely to the surprisingly wide variety of (putative) laws supplied by current science and to the complexity of the relations between those putative laws and regularities and causes.