Exclusive Company: Only and the Dynamics of Vertical Inference ...

12 Only and the Dynamics of Vertical Inference
Thus, a claim about only + CN is simply not equivalent to a claim about all
and only the members of a given set, a fact rendered explicitly in (28a),
excerpted from an Internet posting on lactose intolerance:
(28) a. Only humans and not even all humans are genetically equipped to
drink milk into adulthood,
b. Humans are genetically equipped to drink milk into adulthood.
The corresponding claim in the prejacent, (28b), is not interpreted existentially
but universally or at least generically, and again represents a stronger commitment
than is licensed by the assertion of (28a).
Of course, an individual-level only predication may be consistent with the
corresponding all and only statement, as in (29), but the point is that (29b, c) are
not valid consequences of (29a), even though they happen to be true. What
follows from (29a) is not (29b) or (29c), but (29d). 17
(29) a. Only birds have feathers.
b. All birds have feathers.
c. All and only birds have feathers.
d. All feathered things are birds.
In recognizing the mutual convertibility of exclusives and universals, we
obtain the equivalences of (30), preserving monotonicity orientations for the
corresponding argument positions as indicated. 18
(30) a. only As are Bs all BsareAs every (B)(A)
*— DE environments —'
non-DE environments —I
Finessing the issue of existential import, only behaves like an upward monotone
determiner that combines with a focus argument to form a downward
monotone quantifier, while every /all is a downward monotone determiner that
combines with a restrictor to form an upward monotone quantifier. We can
represent the correspondence in (30) schematically by three-dimensionalizing
the traditional Aristotelian square of opposition:
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