فلسفه‌ی زبان موریس: پنج؛ انواع طبیعی
در این فصل به انواع طبیعی پرداخته می‌شود. یکی از خصوصیاتِ مثبتِ کتابِ موریس این است که بحثِ ترم‌های انواع طبیعی کمابیش به صورتی مفصل مورد بحث قرار گرفته است (مثلاً در مقام مقایسه در کتاب‌های میلر، لایکن و کِمپ این بحث به صورتی موجز و در حد دو یا سه صفحه مورد بحث قرار گرفته است). منابع اصلی مربوط به این فصل اینها هستند:
1- Naming and Necessity, Kripke, lecture 3;
2- Meaning and Reference, Putnam.
قسمت اول: مقدمه
Saul Kripke’s arguments against description theories of names inaugurated a revolution in the philosophy of language. One of the first acts of that revolution was an application of similar arguments against a similarly descriptive theory of another sort of expression – so-called natural-kind terms. Kripke himself claimed that natural-kind terms are rigid designators. In this, he was supported by the semi-independent work of Hilary Putnam. Kripke and Putnam together are acknowledged as the creators of a new theory of such terms.
Natural-kind terms differ from proper names in this: whereas proper names pick out individuals, natural-kind terms pick out kinds. Favorite examples are ‘tiger’ and ‘water’.
What makes a kind natural? There are two based conceptions of nature which seem to be at play in the focus on natural-kind terms:
(SRN) A natural kind is a kind about which some natural science is authoritative.
What is natural science? We will have a list – physics, chemistry, biology – and we will have in mind certain contrasts – with art and with human sciences.
The other conception of nature is perhaps more fundamental:
(RKN) A natural kind is a kind whose identity as a kind is fixed by reality, and not by human interests or concerns.
Someone may concern, of course, link the two conceptions. Indeed, it might be held that the distinctive point and value of natural sciences is that they tell us how reality is in itself. This kind of view is often known as naturalism, and sometimes as scientific realism.
One way the issue of natural-kind terms is important is that it connects philosophy of language with metaphysics.
قسمت دوم: دیدگاهی لاکی دربابِ ترم‌های انواع طبیعی
Locke: “The nominal Essence of Gold is that complex Idea the word Gold stands for, let it be, for instance, a body yellow, of a certain weight, malleable, fusible, and fixed.”
This remark and others in the surrounding text has suggested that Locke himself held a counterpart – for the case of natural-kind terms – of the description theory of names which Kripke is concerned to undermine in the earlier of Naming and necessity. But we can reasonably describe the view Kripke and Putnam attack as broadly Lockean.
We can state the core of a Lockean theory of natural-kind terms, as follows:
(LK) The meaning of a natural-kind term is determined by what is believed to be definitive of the kind in question.
And we can lay out the commitments of such a theory, as follows:
(LK1) If ‘K’ is a natural-kind term, there is a family of things associated with ‘K’, an appropriate part of which is believed to be true of members of K and only members of K;
(LK2) If ‘K’ is a natural-kind term, then if an appropriate part of what is believed to be true of members of K is, in fact, true of something, then that thing is indeed a member of K;
(LK3) If ‘K’ is a natural-kind term, then it is a priori that an appropriate part of what is believed to be true of members of K is, in fact, true of members of K;
(LK4) If ‘K’ is meaningful natural-kind term, then it is necessary true that an appropriate part of what is believed to be true of members of K is indeed true of members of K.
Locke seems generally to endorse an individualist conception of language: each person is the authority over the use of her own terms; a word in one person’s mouth can signify only that person’s conception of things. It is this individualist theory which is the target of the most direct of Kripke’s and Putnam’s criticism.
Take (LK1) first. Putnam says that he cannot tell the difference between elms and beeches, and indeed claims that there is no difference between his concept of an elm and his concept of a beech. So (LK1) looks false.
(LK2) is similarly doubtful. Suppose that what I think is definitive of tigers is just that they are large carnivorous quadrupeds of cat-like appearance, tawny yellow in color with blackish transverse stripes and white belly. Kripke claims, plausibly, that there could be something of just this appearance which was of a different species, and did not count as a tiger. The crucial thing here is that the conception of members of a natural kind which ordinary speakers possess seems to relate principally to relatively superficial appearances. What Kripke’s point suggests is that, intuitively, we do not regard such superficial appearance as really determining what counts as a genuine member of a natural kind. Instead, the job is done by something which we might hope that a biologist would know, but most of us are ignorant of.
This is one of the points of Putnam’s ‘Twin-Earth’ example. Putnam imagines that there is another planet somewhere else in the universe, which he calls Twin Earth. Twin Earth is qualitatively indistinguishable from earth, at least in relatively superficial appearance: that is to say, if you were instantaneously transport there, you wouldn’t notice the difference. Despite all this superficial similarity, there is a fundamental difference between Earth and Twin Earth: whereas the chemical composition of the stuff in Earth rain, Earth rivers, Earth lakes, which we call ‘water’, is H2O, the chemical composition of the similar stuff on Twin Earth, which the Twin-Earthians call by similar-sounding name, is something quite different – XYZ, let’s say. Putnam claims that the stuff on Twin Earth, despite being superficially indistinguishable from water is not really water. What Putnam is claiming here is that what counts as water is not determined by what ordinary speakers know. It is the knowledge of the scientist which is decisive, not the concepts which ordinary speakers have.
Take (LK3). Kripke shows how we can raise doubt this by considering two kinds of possibility: the possibility that we might have been subject to some kind of illusion when we encountered those members of the kind on which our conception of the kind is based; and the possibility that the members of the kind we have encounter were in fact abnormal.
Now take (LK4). We might identify water as the liquid which falls in rain, which flows in rivers, and which fills lakes and seas. This might be how we fix the reference of the term ‘water’, but it is surely not necessary that water does this.
Kripke and Putnam themselves seems to be more interested in a Lockean claim which looks almost the converse of (LK4). We might formulate it like this:
(LK5) If ‘K’ is a natural-kind term, then nothing is necessarily true of members of K as members of K other than appropriate part of what is believed to be true of members of K, or what follows logically from that.
This claim derives from a general trend in empiricism. A crucial commitment of empiricism is the view that we cannot have any real knowledge of the world beyond what we can gain from experience. Within this basic philosophical approach, Hume made the following claim: we cannot literally perceive that something is necessary.
If necessary derives from our way of thinking about things, rather than from the things themselves, it seems that what is necessarily true of a natural kind can only derive from the way we think of the kind. Kripke and Putnam are concerned to deny (LK5) and the associated conception of necessity as being derived from our way of thinking of things. Consider the following pair of sentences, for example:
(1) Gold is the element with atomic number 79;
(2) Water is H2O.
They claim that statements like these are necessary – at least if they are true at all. Although they are necessary, (1) & (2) are a posteriori. In insisting that (1) and (2) are necessary, Kripke and Putnam are attacking the empiricist conception of necessity which led people to conflate the epistemic and the metaphysical in first place.
Take (1) for example. It seems that (1) can only be necessary if both of the following are true:
(1a)The predicate ‘x is the element with atomic number 79’ applies to that stuff in all possible worlds;
(1b)The term ‘gold’ picks out that stuff in all possible worlds.
If (1) is true, then it seems that (1a) must be true. But (1b) is just the claim that ‘gold’ is a rigid designator. What this show is that the claim that (1) and (2) are necessarily true, depends on the claim that ordinary natural-kind terms are rigid designators.
قسمت سوم: چگونه ترم‌های انواع طبیعی می‌توانند نشانگرهای صلب باشند؟
According to the Kripke-Putnam view, natural-kind terms like ‘gold’, ‘water’, and ‘tiger’ are rigid designators: they designate the same kinds in all possible worlds. They seem to offer an account of their rigidity which is parallel to Kripke’s picture of how proper names work.
In the case of gold, Kripke imagines a ‘hypothetical’, though ‘admittedly somewhat artificial’ baptism, carried out by means of some such declaration as this: ‘Gold is the substance instantiated by the items over there, or at any rate, by almost all of them’. Putnam imagines that I give what amounts to an ‘ostensive definition’ of water as something like ‘the liquid which has such and such superficial properties in the actual world’. Kripke’s ‘baptism’ and Putnam’s ‘definition’ look just like the different ways in which Kripke imagined the reference of a proper name might be fixed.
This might then be thought to suggest that the later uses of natural-kind terms designate the relevant kinds in virtue of being historically connected to the first, introductory uses. That might suggest that natural-kind terms, like proper names, are directly referential. And it might then seem that this non-descriptive directness is what explains the rigidity of natural-kind terms, just as it seems to in the case of proper names.
منابع بیشتر
1- The meaning of ‘meaning’, H. Putnam;
2- Natural Kinds, D. H. Mellor,
3- Putnam’s Theory on the Reference of Substance Terms, E. Zemach;
4- Natural Kind Terms and Recognitional capacities, J. Brown;
5- Natural Kind Terms: A Neo-Lockean Theory, A. D. Smith;
6- Beyond Rigidity, S. Soames.
