Full Idea
Quine claims that an unmanifested disposition is explicable in terms of an object having a structure similar to a structure of an object that has manifested the supposed disposition.
Gist of Idea
Explain unmanifested dispositions as structural similarities to objects which have manifested them
Source
report of Willard Quine (Word and Object [1960], §46) by C.B. Martin - The Mind in Nature 07.4
Book Reference
Martin,C.B.: 'The Mind in Nature' [OUP 2008], p.86
A Reaction
This is probably the best account available for the firm empiricist who denies modal features in the actual world. In other words, a disposition is the result of an induction, not a conditional statement.