Generics, Frequency Adverbs, and Probability

sentence is true), or by none of them (in which case it is false). Otherwise,
the sentence will be ruled out as a violation of the homogneity requirement.
Recall that one of the criteria for the admissibility of a history is that
it must continue the relevant part of the actual history. We are now in a
position to say more about this. There are cases where the relevant part of
the actual history is explicitly stated:
(25) a. Moths were (usually) black in the industrial areas of Britain in
the late 19th century (Manfred Krifka, personal communication).
b. Since the last election, foreign affairs have (often) been neglected.
c. In the 52nd century, robots will (never) be welcome in polite
society.
Sentence (25.a) is evaluated with respect to histories continuing the late 19th
century, sentence (25.b) is evaluated with respect to histories which continue
the history from the last election to the present, and (25.c) is evaluated with
respect to histories continuing the 52nd century.
It is important to emphasize that the temporal modifier restricts the
relevant part of the actual history, not the duration of an admissible one.
Sentence (25.a) is not simply about that moths that happened to exist in the
late 19th century, but is lawlike; it implies that if things were today the way
they were in the 19th century, moths would be black today. In an admissible
history, things today (and in the future too), are the way they were in the
late 19th century. Such a history will not be restricted just to the duration
28