• The first of the requirements Lambert and Britten consider is that laws have empirical content. Apart from cases of nonsense, the generalizations they consider that don’t satisfy this requirement are ones that hold in virtue of the meanings of words (like “bachelor” and “unmarried”) that they involve. One way of seeing the problem with these is to note that they don’t really provide explanations because they merely show how the state or event to be explained may be described in different, but equivalent, terms.

• The second requirement, which is considered only briefly, is truth. That this is a requirement if laws are to serve in explanations may seem obvious (how could we explain something if the basis for our “explanation” fails to be the case?). And Lambert and Britten’s consideration of it may only be an expository device since the possibility of “laws” that are only approximately true points to the idea of “lawlikeness”: features of laws that might appear even in statements that are not true.

• The feature of the later sort of most interest to Lambert and Britten is that laws support conditional statements that make claims not only about what happens to be the case but also about “contrary-to-fact” or “counterfactual” conditions. I’ll leave it to Lambert and Britten to introduce this idea, but I’ll note that it falls between mere truth (which might concern only that actual state of affairs and thus be accidental) and the sort of necessity that derives from connections of meaning (as does the necessity of “All bachelors are unmarried”). One of the things that makes the idea of a scientific law interesting, and difficult, is that it seems to involve both necessity and a dependence on empirical evidence.