Abstract

Similarity is a philosophically much-maligned concept. Bertrand Russell claimed that its ineliminability forces on us the admission of at least one universal, thereby undermining nominalism. But even if things must be supposed to be similar if our language functions publicly by way of using finitely many terms repeatedly for purposes of designation, reference, and predication, Russell’s insistence has as such no bearing at all on the epistemological questions of sorting the actual similarities among things and of fixing the grounds on which we may be sure that they are what they are alleged to be. It need not even affect nominalism. Speculation about universals oscillates between the metaphysical and the epistemological. No one doubts that things must be similar in some respect if natural languages behave as they do. But the concession is thought to be a vacuous one precisely because the respect required need never be specified in that admission. On the other hand, it is characteristically said to be epistemologically superfluous because to say that a set of things are similar in respect R is just to say that they are R’s, and to know that—so the argument goes—is to out-flank the original need to inquire whether they are merely similar, thereby restoring the viability of nominalism. This, briefly, is Nelson Goodman’s strategy laid out compellingly in The Structure of Appearance and collected, with explicitly greater scope as far as his own work is concerned but not essentially altered, in a comparatively recent paper. Of course, the legitimacy of terming a set of things R’s, predicatively, invites us to consider whether, on some theory, things really are such. This, the problem of realism, signifies that however vacuous the admission of similarity may be, the putative finding that a set of things are R’s threatens to be epistemically arbitrary unless we have a reasonable theory regarding the validity of so construing them. On Goodman’s account, realism concerns a system’s admitting or not admitting “non-particulars as individuals”—which is to say, Goodman views the issue neutrally as between platonism and nominalism. On that view, “an individual is particular if and only if it is exhaustively divisible into unrepeatable complexes; while an individual is universal if and only if it contains no unrepeatable complex.” The denial of platonism is the denial that there are nonindividuals, not nonparticulars. Alternatively put, “universality is … a matter of multiplicity of instances.” And “repeatability” occurs if a complex “occurs with some two individuals of one category. A color, for example, is repeated if it occurs at two places, even at the same time; and a time is repeated if two qualia of some one kind occur at that time.” Qualia, then, colors for instance, are complexes.