- 著者
-
横路 佳幸
- 出版者
- 日本哲学会
- 雑誌
- 哲学 (ISSN:03873358)
- 巻号頁・発行日
- vol.2018, no.69, pp.259-273, 2018-04-01 (Released:2018-08-01)
- 参考文献数
- 26
The Principle of the Identity of Indiscernibles (hereafter the PII) states that if
any individuals exactly resemble each other, then they are necessarily identical. Intuitively,
the PII seems valid, but Max Black attempted to refute it by introducing
the possibility of a symmetry universe in which two iron spheres c and p can resemble
each other exactly. This counterexample (hereafter BU) seems easy to rule
out using a weak discernibility strategy (hereafter WD) according to which c, being
spatially separate from p and not from c itself, is not indiscernible from p. WD, however,
leads to ‘the presupposition problem’, because obtaining c as spatially separate
from p presupposes the distinctness of c and p. In this discussion, I will give an outline
of a defense of the validity of the PII that evades the presupposition problem
through the elucidation of some aspects of ‘identity’.
In my view, ‘identity’ has two aspects: one is simply self-identity as a universal
monadic property (hereafter identity-1), and the other is identity as an equivalence
relation entailing indiscernibility (hereafter identity-2). The basis or ground for identity-1
obtaining with regard to an individual x can be called the individuator for x,
but it is no wonder that the individuation and articulation of c and p are prior to or
ground for obtaining c as spatially separate from p. So far as the PII is concerned
with identity-1, it may not be valid. However, we can characterize identity-2, following
David Wiggins’s lead, in terms of what is called the sortal dependency of identity-2
and the extended Locke’s Principle (hereafter ELP), according to which, for any
sortal concept F, x falling under F is identical with y falling under F if and only if x
is the same F as y, and x is the same F as y if and only if a) x and y share F and b) x
is not spatially separate from y. If ELP is valid, we can regard BU as merely a general
case to which WD is applied. And if the Wigginsian idea of the sortal dependency
of identity-2 is also right, there is no longer a presupposition problem. I hence conclude that the PII is valid to the extent that it is concerned with identity-2.