 Having distinguished two quite different meanings of these seemingly similar sentence pairs, the question arises: what is the basis of these two interpretations? This is of course a matter of debate, but one important thesis is that it is the predicate that determines which of the two readings the subject will receive, particularly in the case of bare plural generics. In his 1977 dissertation, Greg Carlson argued that the distinction between “stage level” and “individual level” predicates is key here, and proposed that stage level predications give rise to existential readings of bare plurals and indefinite singulars, while individual level ones give rise to generic readings. The distinction between the two types of predicates can be drawn intuitively, and also on the basis of linguistic patterns (Milsark 1974; Carlson 1977; Stump 1985). Semantically, individual level predicates express properties that normally are had by items for quite extended periods, often comprising the items’ whole existence. Stage-level predicates, on the other hand, express properties normally had by items for relatively short time intervals. Some examples of both types are as follows: