Sellars also has a distinctive treatment of scientific laws.  Laws are standardly treated as generalizations; they are distinguished from accidental generalizations because laws have a modal force capable of supporting counterfactuals.  In Sellars’s view, laws are better understood as inference tickets.  Though they have descriptive content, statements of laws serve a different function in our language.  As mentioned above, Sellars treats modals uniformly as material-mode metalinguistic speech expressing the inferential commitments and priorities embedded in the language.  So, saying that it is a law of nature that e.g., the angle of incidence equals the angle of reflection, endorses a certain set of inferences using those concepts.  Furthermore, Sellars does not think of language as a fixed entity.  Indeed, in his conception, the job of the sciences is to methodically revise and replace the resources available for description and explanation.  Conceptual change is the very essence of science.  In his view, laws of nature are proposed connections among concepts or terms that, pending possible empirical disconfirmation, can be rationally attached to the concepts.