Real and nominal definition
As already noted, the concept of definition goes back to Aristotle, who discussed it at a number of points in his voluminous works. One of the most important Aristotelian treatments of definition is to be found in the Posterior Analytics, a treatise devoted to the explanation of the structure of scientific knowledge. As discussed there, a definition (horismos) has two quite different interpretations: ‘in defining,’ says Aristotle, ‘one exhibits either what the object is or what its name means’ (Tredennick 1960: II.7.92b). A definition can therefore be considered either as a sort of summation of the essence or inherent nature of a thing (real definition; Latin res ‘thing’), or as a description of the meaning of the word which denotes this thing (nominal defi nition; Latin nomen ‘name, noun’). Since Aristotle is interested in providing a basis for an understanding of nature, it is the first interpretation which he adopts: a definition of thunder, for example, is not a description of the meaning of the word thunder, but expresses thunder’s essential nature (for Aristotle, the noise of fi re being extinguished in the sky).
Some people have considered that definitions of the underlying nature of objects are the only type of definitions which can be of interest. Diderot, for example, stated that ‘definitions of words differ in no way from definitions of things’ (quoted in Meschonic 1991: 102). And since it is scientific research which is taken to reveal this underlying nature, these definitions will be formulated by scientific disciplines. The influential American linguist Leonard Bloomfi eld stated in a well-known passage that On the other hand, according to Bloomfield, ‘we have no precise way of defining words like love and hate’ (ibid.). On this understanding, therefore, linguistics should appeal to technical scientific disciplines in formulating definitions; the true meaning of a natural language word, according to Bloomfield, is to be identified with the scientific ‘definition’ – or best possible theory – of its denotation. As a result, whenever a scientifically established definition of a denotation is missing, there is, simply, nothing that linguistics can say with any certainty about the word’s meaning. (One problem with this is that scientific conceptions of the nature of objects are continually changing: just think of the current best theory of space, mass, light, or matter in the world view of modern physics, compared to the same notions just a hundred and fifty years ago, before the advent of relativity and quantum mechanics. These scientific developments radically changed our picture of space, mass and so on, but surely didn’t have any effect on our everyday meanings.)
The situations which prompt people to utter speech, include every object and happening in their universe. In order to give a scientifically accurate definition of meaning for every form of a language, we should have to have a scientifically accurate knowledge of everything in the speakers’ world. The actual extent of human knowledge is very small, compared to this. We can define the meaning of a speech-form accurately when this meaning has to do with some matter of which we possess scientific knowledge. We can define the names of minerals, for example, in terms of chemistry and mineralogy, as when we say that the ordinary meaning of the English word salt is ‘sodium chloride (NaCl)’ . . . Bloomfield (1933: 139)
Bloomfield’s view is a serious obstacle to a comprehensive account of meaning, for it is not just ‘abstract’ nouns like love and hate which lack a scientific definition, but the vast majority of the vocabulary of any natural language. There are two reasons for this. The first is that, as we saw in Chapter 1, words like unicorn, time machine and light sabre lack any denotation in the real world but nevertheless have a meaning. Secondly, most of the vocabulary of a language has only a small amount of overlap with terms of the sort which interest empirical science: most of the vocabulary consists of words for a huge variety of objects, processes, relations and states which have no simple analogue in the scientific picture of reality (think of reportage, postpone, ready).
There is another reason, however, to reject Bloomfield’s approach to definition: even in the case of terms like salt which can be associated with a scientific definition, we do not want to say that the scientific definition (‘NaCl’) has anything to do with most speakers’ understanding or use of the word. While this definition might perhaps be satisfactory as a real defi nition of actual salt, it is certainly unsatisfactory as a psychologically realistic one. Thus, people use and understand the word salt even without specialized scientific knowledge; indeed, English speakers’ first exposure to this word will come at an age when the technical scientific knowledge that supposedly defines it is entirely inaccessible. Speakers with training in chemistry may eventually come to understand salt in this way; but this can only happen after they have already acquired the everyday, nontechnical meaning of the word. For these reasons, we will reject Bloomfield’s approach to definition: linguistic semantics aims to defi ne the meaning(s) of a word, not the underlying essence of the object it refers to. It is thus concerned with nominal, not real definition.
Before proceeding further, we need to distinguish two different functions which a nominal definition may fulfil: fixing the meaning of a word so that there can be no ambiguity about its denotation, and bringing about an understanding of the meaning of a word in someone who does not already understand it, typically in order to enable the word to be correctly used. Many actual definitions aspire to fulfil both these functions simultaneously. The two functions are, however, rather different, and they should be kept apart. In order to differentiate between them, let us call the first type of definition extensional definition, and the second type cognitive definition (Figure 2.2). Thus, the definition ‘featherless biped’ is an extensional definition of the noun human, since it accurately identifies all and only the members of the class of humans.
It is not, however, necessarily a very good cognitive definition, since human is not typically conceived of in terms of bipedality or absence of feathers: when we reflect on our concept HUMAN, we are likely to think of many different characteristics – a certain physical form and range of behaviours – before these ones.
