 Moreover, some treat grounding as a quaternary rather than binary relation. One such view is that the grounding relation includes two slots for facts and two slots for modes of presentation of those facts (Jenkins 2011). Another such view is that grounding is contrastive in nature, so it includes two slots for facts and two slots for contrasts of those facts (Schaffer 2012). Consider, again, the claim that [The truckers are picketing] grounds [The truckers are striking]. Depending on the context, we might read the claim as follows: [The truckers are picketing] rather than [They’re working as normal] grounds [The truckers are striking] rather than [It’s not the case that they’re striking]. Schaffer argues that his version of the quaternary view is preferable to the binary view insofar as we can reasonably maintain that grounding is transitive given the former but not the latter (see  §2.3  for further discussion of transitivity). Schaffer also suggests that the contrastive treatment of grounding is plausible insofar as it casts grounding in an apt form to back explanation, which is itself contrastive in nature.