220 ARGUMENTS: MONOTHEISTIC CONCEPTIONSIf Mary knows that her experience of at least seeming to see a tiger is
counterbalanced, then she is justified in not taking it to be evidence that
there is a tiger that she sees.
Suppose that just prior to Mary’s experience she undergoes a strange
change regarding her perceptions that are, or seem to be, of a tiger – a
change that others do not undergo. The change is this: she can never
perceptually confirm There is not a tiger in the garden (or anywhere else).
For whatever reason, she is perceptually incapable of noting the absence of
tigers. Suppose, further, that it is true that:
(E) If it is not possible for anyone to experientially disconfirm
existential claim P, then it is not possible for anyone to
experientially confirm P
and that applied to Mary (E) yields this truth:
(E-Mary) If it is not possible for Mary to experientially disconfirm
existential claim P, then it is not possible for Mary to experientially
confirm P.
Since, by hypothesis, Tigers exist is not experientially disconfirmable by
Mary, it is, by (E-Mary), not experientially confirmable by Mary either. In
such a circumstance, let us say that Mary’s as-if-a-tiger-in-the-garden
experience is compromised relative to There is a tiger in the garden. So we
replace (P2) by:
(P3) If a person S has an experience E which, if reliable, is a matter of
being aware of an experience-independently existing item X, and E
is not canceled or counterbalanced or compromised, then S’s having
E gives S evidence that X exists.
If Mary discovers that she has changed in the way described, and that (E) is
true, she is justified in not taking her experience to be evidence of the
presence of tigers.
Again, suppose someone discovers a proof that shows that there cannot
be any tigers (the notion of a tiger contains a hidden inconsistency) or
there cannot be any tigers in our world (what we know about initial
physical conditions and laws of nature precludes the development of
tigers). If our world cannot contain tigers, either because no world can or
because of particular features of our world, then as-if-there-is-a-tiger
experiences will all be unreliable. Under these conditions, let us say, Mary’s
as-if-there-is-a-tiger-in-the-garden experience is contradicted. Hence
goodbye to (P3) and hello to: