Comments

Comments Nelson Goodman The Journal of Philosophy, Vol. 63, No. 11, The New Riddle of Induction. (May 26, 1966), pp. 328-331. Stable URL: http://links.jstor.org/sici?sici=0022-362X%2819660526%2963%3A11%3C328%3AC%3E2.0.CO%3B2-2 The Journal of Philosophy is currently published by Journal of Philosophy, Inc..

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it must not have the notion of lawlikeness already built into its account of logical form.

JOHNR. WALLACE WESTERNRESERVEUNIVERSITY

CASE INSTITUTE

OF TECHNOLOGY

COMMENTS Since these papers come to me not long before press time, and since more detailed discussions of at least two of them are in prospectll I shall comment only briefly and on a few salient points. All three papers make some reference to an objection or question attributed to D,onald Davidson: Doesn't my treatment err by ruling out as unprojectible such perfectly acceptable statements as :

H I All emerubies are gred (where an emeruby is an emerald examined before t or a ruby not 'so examined, and anything is gred if it is a green thing examined before t or a red thing not so examined) ? Let us remember that truth of a statement by no means implies projectibility. If our evidence here consists entirely of emeralds examined before t and found to be green, then H1 is clearly unprojectible, and is properly eliminated (in two steps) by our rules. If our evidence consists entirely of rubies examined before t and found to be red, then, since such rubies are not emerubies, the hypothesis is entirely unsupported. If our evidence consists of emeralds examined before t and found to be green and rubies examined before t and found to be red, then both the following are projectible:

Hz All emeralds are green

H 3 All rubies are red.

Now of course H I is true if H z and H3 are; but this is not to say that H1 is projectible if Hz and H 3 are. Obviously, many consequences of projectible hypotheses are not themselves projectible. I n summary, however true H1 may be, it is unprojectible in that positive instances do not in general increase its credibility; emeralds found before t to be green do not confirm H I . I n the second edition of Fact, Fiction, and Forecast, I wrote (p. 96, n) : "Elimination of a hypothesis by means of any principle is of course always overruled where that hypothesis follows from some hypothesis that entirely escapes elimination. " " Elim1 A discussion of Mr. Wallace's paper by Marsha Hanen and of Mrs. Thornson's paper by Robert Schwartz and James Hullett should appear soon. I am heavily indebted to all three for help in preparing the above remarks.

ination" of a hypothesis consists of refusing to accept it as true. When the elimination is on grounds of relative unprojectibility, the overruling in question here amounts to canceling that refusal, not to classifying the hypothesis as lawlike. Although the hypothesis may now be legitimately accepted, and may be supported, unviolated, and unexhausted, it is not therefore projectible in the sense of being lawlike. Some confusion might be prevented by using 'lawlike' rather than 'projectible' in such contexts. Mr. Jeffrey drives home the point I urged in my earlier articles: that the various Hempel and Carnap definitions of confirmation work only to the extent that we apply them to or build in just the right predicates and that these treatments provide no general criterion of what the right predicates are. While Carnap is content to leave the selection to particular extrasystematic decisions, I consider a theory of confirmation deficient unless it incorporates a general formulation of the distinction between the right (or projectible) predicates and the wrong ones. To rest with particular extrasystematic judgments here is to raise the question why we seek a systematic treatment of confirmation at all rather than resting with judgments of the validity of each particular inductive inference. I n saying that projectibility depends not merely upon syntax but upon meaning, Mr. Jeffrey is not claiming that projectibility can be defined in terms of some general semantic property of predicates but saying only that judgment of the projectibility of a particular predicate requires knowing the interpretation as well as the spelling of the predicate. Once we have chosen a confirmation-function that assigns degrees of projectibility in accord with our particular judgments-that is, once we have built in the right degree of projectibility for each predicate-then we may attempt to retrieve by definition within the system the distinction between projectible and nonprojectible predicates that has been put there. A surprising result of Mr. Jeffrey's paper is how difficult this seemingly trivial task proves to be. He finds that the semantic definition he first proposes makes 'grue' projectible, and he has therefore to provide a more complex pragmatic definition. A theory of meaning that goes beyond the theory of reference is required here; and all this is directed not toward any general definition of projectibility but only toward retrieving a distinction already built ad hoc into a given system. Mrs. Thomson seeks a definition of projectibility in terms of the notoriously obscure notion of observability. 'Green' is an observation-predicate while 'grue' is not, she says, because we

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can tell whether a thing is green but not whether it is grue by simply looking at it in a good light. This, to say the least, does not submit to easy generalization. An object is not spherical if it looks spherical in good light, or even from a good angle, but rather if it looks round from all angles. To arrive at any good general definition of the class of observation-predicates would be exceedingly difficult. I n the second place, judging from what seem to be reasonably clear cases, the line betveen observation-predicates and others does not coincide with the line betveen projectible and nonprojectible predicates. 'Conducts electricity' and many other predicates more remote from unaided momentary inspection are plainly projectible. Thus, even given an adequate definition of observability, definition of projectibility in terms of it would be at best a hard task. In the third place, I am not quite sure just what Mrs. Thomson is claiming. Is she saying merely that English-speaking people normally do not apply the predicate 'grue'-or apply it correctly -after simply examining a thing in good light? That is a sheer truism. Or is she saying that no human being can so apply 'grue'? And if so, is she claiming that no human being in fact can do this or that no human being possibly could? In the former case, she would be saying little more than that the way humans behave must be due to some characteristic they happen to haveand this again is an empty truism. The stronger claim, that no human being could be otherwise, is (in the absence of any argument as to the limitations implied by 'human') utterly groundless in view of the fact that we can readily construct a machine that will apply 'grue' correctly upon being shown an object in a good light.2 Finally, even if Mrs. Thomson could give a general and acceptable definition of observability, could define projectibility in terms of this, and could show that these distinctions are rooted in some essential features of the human organism-and these would be three very large orders indeed-nothing here would be incompatible with a definition of projectibility in terms of entrenchment; rather we would have a psychological explanation of the facts of entrenchment. But I cannot see that Mrs. Thomson's patient and earnest effort makes any real progress in this direction. Mr. Wallace charges that my treatment of projectibility transgresses the boundaries of "quantificational logic " ? At first sight, this carries the ominous intimation that I, of all people, have been

"

2 Compare the description of a "b-meter " i n my Positionality and Pictures" i n the Philosophical Review, 69, 4 (October 1960) : 523-525.

COMMENTS

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caught trafficking with intensions, modalities, non-truth-functional connectives, and referential opacity. But as we read on we find that my sin amounts to refusing to consider equivalent hypotheses identical. To this, I confess eagerly. For me a hypothesis is a statement, and an equivalent hypothesis may be a different statement. Whether in the context of inductive or deductive logic, a statement and its contrapositive, for example, are equivalent but not identical. Once this is recognized, and it seems plain enough in my writing, all the difficulties so painstakingly detailed by Mr. Wallace evaporate. I n the primary sense of confirmation, whatever confirms a hypothesis confirms every equivalent hypothesis; but equivalent hypotheses may nevertheless differ in many other respects: in their antecedents and their consequents, in their positive and negative instances, in their evidence classes and projective classes, etc. etc. Sometimes, as in the case of a hypothesis and its contrapositive, they may have different contraries; and this leads to an interesting and pertinent secondary version of confirmation such that what so ("selectively") confirms a hypothesis does not always so confirm an equivalent hypothesi~.~ Along the way, Mr. Wallace raises an incidental point that calls for some clarification. He argues that to deny that 'grue emerald' is as well entrenched as 'emerald' is to deny that the two are coextensive and, hence, to decide without evidence that "All emeralds are grue emeralds" is false. But comparisons of entrenchment, in my treatment of projectibility, are always relative to the occurrence of the two predicates in parallel positions in a pair of hypotheses, and are conditional in character. Consider parallel hypotheses of the following sort: All so-and-so's are emeralds All so-and-so's are grue emeralds. If these conflict, then the consequent-predicates are not coextensive and the first is obviously much better entrenched than the second. If the hypotheses do not conflict, we need not choose between them. Extensional divergence of the two predicates is not asserted categorically; rather we say that unless the two are coextensive, the first is the much better entrenched. Let me repeat in closing that I by no means suppose that my brief and almost impromptu remarks do full justice to any of these thoughtful papers.

NELSONGOODMAN 3 See Israel Soheffler's The Anatomy of Inquiry (New York: Alfred Knopf, 1963), pp. 287-289.

A.