Real Ceteris paribus Laws
Although there is an ongoing controversy in philosophy of science about so called ceteris paribus lawsóthat is, roughly, about laws with exceptionsóa fundamental question about those laws has been neglected (ß2). This is due to the fact that this question becomes apparent only if two different readings of ceteris paribus clauses in laws have been separated.
The first reading of ceteris paribus clauses, which I will call the epistemic reading, covers applications of laws: predictions, for example, might go wrong because we do not know all the relevant factors which are causally effective in relevant situation. The second reading, which I will call the metaphysical reading, is concerned with the laws themselves and their possible exceptions (ß3). It is this latter readingóand the funda- mental question associated with itówhich has been neglected due to the confusion of the two readings (ß4): if we leave epistemic issues aside is there at all conceptual space left for a notion of laws of nature which allows the laws themselves to have exceptions? I call a law with exceptions in this sense, if such there is, a real ceteris paribus law.
To tackle this question, I distinguish grounded laws from non-grounded laws (ß5). A grounded law is, roughly, a law about structured entities where the properties of the parts of that structure figure themselves in laws of nature (ß6). I will claim that, since the substructure of such an entity can be damaged, grounded laws themselves can face exceptions. Hence, they are candidates to be real (metaphysical) ceteris paribus laws in the sense of my central question. I will discuss grounded laws and their exceptions in detail (ß7, ß8, ß9).
For reasons of space, the further question whether we can even have a notion of fun- damental (non-grounded) laws that allows for exceptions cannot be discussed here. I will, however, give a positive answer and also outline how I have argued for that claim elsewhere (ß10).