RICHARD L. MENDELSOHN

PLANTINGA

ON PROPER

NAMES AND PROPOSITIONS*

(Received 16 November, 1977) In The Nature o f Necessity, x Alvin Plantinga has proposed a novel solution to Frege's famous problem of explaining the difference in 'cognitive value' between ra = a-1 and true r-a = ~ , when a and/3 are both proper names. 2 Frege had identified a level of sense, distinct from reference, at which ot and/3 might differ, so that rot = ot7 and true tot = ~ could express different propositions. Plantinga, however, rejects Frege's view that proper names of the same object can differ in this way. On his view, when ot and/3 are both proper names, rot = otq and true rot = ~ must express the very same proposition. The burden of his solution, then, is to show that this position is not, as so many philosophers have thought, absurd. I will argue that Plantinga has not succeeded. Plantinga maintains that 'Hesperus' and 'Phosphorus', being proper names of the same object, both express the same essence, and that, as a result, the two sentences, (1)

Hesperus =Phosphorus,

and

(2)

Phosphorus = Phosphorus,

both express the same proposition. Anyone who knows that Phosphorus = Phosphorus therefore knows that Hesperus = Phosphorus. And since everyone knows that Phosphorus = Phosphorus, Plantinga claims, then, contrary to common belief, the Babylonians cannot be credited with having discovered that Hesperus = Phosphorus. For this, i.e., that Phosphorus = Phosphorus, is something that had already been widely known. So what truth lay hidden from the Babylonians until their justly celebrated discovery? ... the Babylonian astronomers were ignorant of the fact that (20) Hesperus is identical with Phosphorus and (20') Phosphorus is identical with Phosphorus express the same proposition. (p. 85) Philosophical Studies 43 (1978) 211-218. All Rights Reserved Copyright 9 1978 by D. Reidel Publishing Company, Dordrecht, Holland

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Plantinga supposes, for simplicity, that the Babylonians spoke English and that they understood the sentences well enough: theirs was not linguistic or conceptual inadequacy. Nevertheless, "they did not really know what proposition was expressed by [(1)]" because "they did not know that [(1)] expresses the proposition that Phosphorus is identical with Phosphorus." (p. 85) But how can Plantinga hold that the Babylonians understood (1) if "they did not know what proposition [it] expresses?" (p. 85) I think this is an overstatement. 3 Plantinga argues that they did not really know what proposition (1) expresses - and this means, I take it, that they did know in one sense, but not in another. The sense in which the Babylonians did not know what proposition (1) expresses is clear: they were unaware of the truth of (3)

'Hesperus = Phosphorus' expresses the proposition that Phosphorus = Phosphorus.

Plantinga is not as explicit about the sense in which they did know what proposition (1) expresses, but I would suggest, as an absolute minimum, that the Babylonians were aware of the truth o f (4)

'Hesperus = Phosphorus' expresses the proposition that Hesperus = Phosphorus.

For, surely, every instance of the disquotation schema, (5)

'...' expresses the proposition that ....

where the same English sentence fills both spaces, expresses a truth, and one that is obvious to anyone who understands what the sentence expresses. Indeed, if I understand Plantinga correctly, it is in their knowledge of another instance of (5), namely, (6)

'Phosphorus = Phosphorus' expresses the proposition that Phosphorus = Phosphorus,

that he locates the needed contrast to explain the difference in attitude toward (1) and (2). The Babylonians knew that 'Phosphorus = Phosphorus' expresses that Phosphorus = Phosphorus, and they knew this proposition to be true, so they assented to (2); but they did not know that Phosphorus = Phosphorus was also expressed by 'Hesperus = Phosphorus', so they did not assent to (1). They knew what proposition (1)expresses, namely, that Hesperus = Phosphorus; but they did not know that that proposition, i.e.,

PLANTINGA

ON P R O P E R

NAMES AND PROPOSITIONS

213

that Hesperus = Phosphorus, is the same as the proposition that Phosphorus = Phosphorus. The Babylonians surely knew, on the other hand, that the proposition that Phosphorus = Phosphorus is the same as the proposition that Phosphorus = Phosphorus. So, for Plantinga, (7)

(The proposition that Hesperus = Phosphorus) = (the proposition that Phosphorus = Phosphorus),

must express a different proposition from that expressed by (8)

(The proposition that Phosphorus = Phosphorus)= (the proposition that Phosphorus = Phosphorus).

But then, (1) and (2) would have to express the same proposition because 'Hesperus' and 'Phosphorus' express the same essence, but not (7) and (8). I will argue that Plantinga is mistaken here: (7) and (8) express the same proposition, just as (1) and (2) do. Proper names, Plantinga says, express essences: The proper name 'Aristotle' expresses an essence of Aristotle. It therefore expresses a property P that is instantiated by the same object in every world - in every world in which P is instantiated, of course; for there are worlds in which Aristotle does not exist. What is characteristic of proper names, then, is that the properties they express are instantiated by the same objects in every world. In this regard they are to be contrasted with descriptions such as 'the first man to climb Ranier'. This latter, indeed, expresses a property - the property of being the first man to climb Ranier. But that property is not an essence; for different objects exemplify it in different worlds (pp. 80-1) Of course, some definite descriptions also express essences: 'the square root of 81', e.g., expresses a property that is exemplified by the same object, the number 9, in every possible world (in which the number exists). So Plantinga's notion of a singular term that expresses an essence coincides in essentials with Kripke's more well known notion o f a rigid designator. 4 Supposing that 0~ and codenotational fl express essences, it does not follow (as Plantinga believes) either that they express the same essence or that r a = a7 and r a = ~ express the same proposition. The appeal to intuition is insufficient. It is surely doubtful whether 'the square root of 81' and 'the number 9' express the same property, and equally, whether 'the number 9 = the number 9' and 'the number 9 = the square root o f 81' express the same proposition. Nor is there any technical justification for these claimS, s In fact, Plantinga never attempts even to argue for any of this. I am inclined to believe that he decided to leap over these difficulties and confront Frege's

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problem directly, as this is the most serious obstacle threatening the plausibility of his view. We need not therefore trouble ourselves with the justification for these claims any longer. Let us simply proceed to state Plantinga's substitution principles. Let Sa be a sentence containing the singular term a, and let Sot/J3 result upon replacing c~ at one or more of its occurrences in Sa by/3. Then, Plantinga appears to be assuming, roughly:

(i)

If a and /3 express the same essence, and if a occupies purely referential position in Sa, then Set and Sail3 express the same proposition (i.e., the proposition that Set = the proposition that

Sel~). (I) underpins the claim that (1) and (2) express the same proposition, but it cannot sanction the inference (p. 84) of (9)

The Babylonians believed that Hesperus = Phosphorus,

from (10)

The Babylonians believed that Phosphorus = Phosphorus,

because 'Phosphorus' does not occupy purely referential position in (10). However, this inference is adequately handled by: (II)

If St~ and Sot/J3 express the same proposition, then replacing one by the other in a context governed by a verb of propositional attitude preserves truth.

(I) and (II), I believe, form the core of Plantinga's position. In one passage, however, Plantinga assumes a strengthened version of (II), on which sameness of proposition, not merely sameness o f truth value, is preserved under the substitution: If 'Hesperus' and 'Phosphorus' are proper names of Venus, however, then [(1)] expresses the very same proposition as [(2)]. And if [(1)] expresses the very same proposition as [(2)], then the Babylonians did believe the former, since they believed the latter. How, then, can we account for their sincere claim to reject [(1)17 Shall we suppose that they believed [(1)] - the proposition - but did not know or believe that they believed it? No; for no doubt they knew they believed !(2)1; and !(1)1 is [(2)1. (P. 84) That is, since (1) and (2) express the same proposition,

PLANTINGA

(11)

ON P R O P E R

NAMES

AND PROPOSITIONS

215

The Babylonians believed that they believed that Hesperus --Phosphorus,

and (12)

The Babylonians believed that they believed that Phosphorus = Phosphorus,

must have the same truth value. But, for (11) and (12) to have the same truth value, (9) and (10) must express the same proposition. (II) only gives us that they have the same truth value. But Plantinga's position would immediately collapse with this strengthened principle. Plantinga must explain how (1) and (2) express the same proposition when (3) and (4) (and (7) and (8)) do not, the only relevant difference between the cases being that, in (1) and (2), 'Hesperus' and 'Phosphorus' occur in an extensional context, while in (3) and (4), they do not. The strengthened version of (II) blurs this distinction: taking 'express' to be our verb of propositional attitude, (3) and (4) would have to express the same proposition since (1) and (2) do. Even with (I) and (II) alone, however, Plantinga runs into serious difficulties. He says that the Babylonians failed to realize that (1) and (2) express the same proposition because they were ignorant of the truth of (3). And why were they so ignorant? It was not that the Babylonian linguistic competence was insufficient, not that they did not grasp or apprehend the proposition expressed by the sentence (20) Hesperus is identical with Phosphorus, that is, the proposition that Hesperus is identical with Hesperus. There may have been people who had never studied astronomy or looked at the night sky, for example. But this was not the Babylonian trouble. Their problem was that they did not realize that (20) expresses the proposition that Hesperus is identical with Hesperus; and they were not apprised of this fact because they did not know that Hesperus bore the name 'Phosphorus' as well as the name 'Hesperus'. (p. 87). This answer will not do. Plantinga holds that (13)

The Babylonians knew that Hesperus was named 'Hesperus',

expresses a truth, and that (14)

The Babylonians knew that Hesperus was named 'Phosphorus',

does not. But if he grants (13), he should also grant (15)

The Babylonians knew that Phosphorus was named 'Phosphorus'.

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And if so, then since (p. 84) "Hesperus was named 'Phosphorus' " and "Phosphorus was named 'Phosphorus' "express the same proposition, by (II), (14) must also express a truth. There is worse trouble for Plantinga. The term 'the proposition that Hesperus = Phosphorus' occupies purely referential position in (4), so that, given the truth, say, of (16)

(The proposition that Hesperus = Phosphorus) = (the proposition expressed by sentence (1) of this paper),

we can, by (I), infer (17)

'Hesperus=Phosphorus ' expresses the proposition expressed by sentence (1) of this paper,

from (4). Unlike the situation with regard to (3) and (4), however, there is no doubt about whether (4) and (17) express the same proposition. For one would hardly think that 'the proposition that Hesperus = Phosphorus' is synonymous with 'the proposition expressed by sentence (1) of this paper'. In comparison with this description, both 'the proposition that Hesperus = Phosphorus' and 'the proposition that Phosphorus = Phosphorus' come as close as one is likely to get to a proper name of a proposition. To be sure, they differ from 'Charles' and 'James', but they are sufficiently similar to other expressions Plantinga claims to be proper names to be classed along with them. For example, Plantinga says: ... 'wisdom' enjoys the same semantic properties that a proper name of wisdom would have, even if it is not properly called a proper name of that property. For present

purposes, therefore, I shall extend the use of 'proper name' and reckon such terms as 'masculinity', 'being composite', 'open-hearted friendliness', being more than seven feet tall', and the like, as proper names of the properties they denote; in this regard they contrast with such terms as 'Jabbar's most striking property' and 'David's most endearing property'. (p. 31) In the same way, 'the proposition that Hesperus = Phosphorus' contrasts with 'the proposition expressed by sentence (1) of this paper', and it should be counted a proper name of a proposition. Indeed, 'the proposition that Hesperus = Phosphorus' seems to be a singular term that expresses an essence: it designates the same proposition in every possible world (in which it exists). It is very different from a definite description like 'the proposition expressed by sentence (1) of this paper'. For although the proposition expressed by sentence (1) of this paper is none

PLANTINGA ON PROPER NAMES AND PROPOSITIONS

217

other than the proposition that Hesperus = Phosphorus, it might not have been: it is only a contingent fact about that proposition that it is expressed by sentence (1) o f this paper. But the proposition that Hesperus = Phosphorus that very proposition - could not have been other than the proposition that Hesperus = Phosphorus, i.e., the proposition it in fact is. That is to say, 'the proposition that Hesperus = Phosphorus' expresses an essence. If I am right, however, then 'the proposition that Hesperus = Phosphorus' and 'the proposition that Phosphorus = Phosphorus' express the same essence, so by (I), (3) and (4) must express the same proposition, and, finally, (7) and (8) must express the same proposition. And this is just what I claimed would happen on Plantinga's view. One final comment. I have not considered the possibility that Plantinga might deny that the Babylonians were aware o f the truth o f (4). Plantinga gives no hint of adopting such a radical course in his treatment of Frege's problem, although there are indications of such leanings in his treatment of a related issue elsewhere, 6 and, if m y arguments here are correct, he might ultimately have to adopt it if he were to persist in maintaining that (1) and (2) express the same proposition. But aside from the extraordinarily difficult problems Plantinga would have in trying to make such a view plausible, he would still have to come up with a solution to Frege's problem. For, as we have seen, Plantinga needs to make use o f the disquotation schema in order to explain why the Babylonians had demurred at (1) while assenting to (2).

Lehman College of the City University of New York NOTES * The research for this paper was supported in part by The Research Foundation of the City University of New York, grant #11768, for which I am grateful. I would also like to express my thanks to Richard L. Cartwright for many helpful discussions on the topic of proper names and for his criticism of earlier drafts. 1 Oxford University Press, Oxford, 1974. All page references will appear in the text. 2 Gottlob Frege, 'On Sense and Reference,' transl, by Max Black, in Translationsfrorn the Philosophical Writingsof Gottlob Frege, ed. by Peter Geach and Max Black (Blackwell, Oxford, 1960), pp. 56-78. In 'Plantinga, Proper Names and Propositions', Philosophical Studies 30 (1976), 409-412, Diana F. Ackerman takes Plantinga somewhat more literally than I do. Although I agree with much of what she says, I am unable to assess her arguments, in large measure because she never makes clear either her position or Plantinga's with regard to th.e disquotation scheme.

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4 See Saul Kripke, 'Naming and Necessity', in Semantics and Natural Language, ed. by Gilbert Harman and Donald Davidson (D. Reidel, Dordrecht, 1972), pp. 2 5 3 - 3 5 5 , 763-769. 5 There is a misconception current that on Kripke's view, Sa a n d S a / ~ must express the same proposition when a and ~ both rigidly designate the same object. See, e.g., G. W. Fitch, 'Are There Necessary A Priori Truths?',Philosophical Studies 30 (1976), 2 4 3 - 2 4 7 . This is not so. When a and ~ both rigidly designate the same object, i.e., when they refer to the same object in every possible world (in which the object exists), then ~ and # are interchangeable in contexts governed by a necessity operator, preserving truth. It does not follow from this that a and ~ can be interchanged anywhere and preserve truth: in epistemic contexts, e.g., for which Kripke claims the heuristic o f possible worlds is inappropriate, the interchange o f a and ~ might very well not preserve truth. 6 Commenting on Kripke's example of a sentence that expresses a contingent a priori truth, 'S is one meter long at t', he says: Suppose I have never seen S and hold no views as to its length. I propose none the less to use 'one metre' as a rigid designator o f the length, whatever it is, that S actually displays at t. After thus determining the reference o f 'one metre', I know that the sentence'S is one metre long at t' expresses a truth in m y language; the truth it does express, however, is one I neither know nor believe. So my thus determining the reference o f 'one metre' is not sufficient for m y knowing a priori that S is one metre long. (10.9). Plantinga is denying that, in the situation described, one knows t h a t ' S is one meter long at t' expresses the proposition that S is one meter long at t. It is not clear to me, however, whether he is not also denying that one has grasped the proposition expressed by 'S is one meter long at t'. The Hesperus/Phosphorus case is, at any rate, very different from this one. For in the Hesperus/Phosphorus case, there is no stipulation o f reference, the speakers are already familiar with the referents sufficiently to identify them (under certain circumstances, but not, of course, all), and the speakers also have a good grasp o f the relevant proposition.