are necessary for the concept in question are missing, or there are some disqualifying features present. Defining an object ostensively is not simply a 'ceremony'; the act works in a context in which there are public constraints on the use of the concept. But in the case of private
ostension, that context is missing. All we have left is the 'ceremony'.
Suppose a child was trying to learn the names of the birds in her garden. She might hit upon the following strategy. In order to fix the concept under which any bird falls, she would concentrate her attention on it and name the bird. Then, consulting the bird-spotter's book, a mere exchange of name would be all that was required. The concept, it might seem, would already be in place, ostensively defined. Suppose she were to perform this ceremony, and later came upon a picture which seemed absolutely right to her. The child thinks "Ah, yes. The name of the bird fixed by my private ostension is House Wren". Would that necessarily fix the name as the right one? Surely not. Suppose, further, that on turning the page, she came across the Carolina Wren, the Bewick Wren and the Marsh Wren. Although they all look a little different to one another, and to the House Wren, they all seemed equally right. Indeed it might have been a Gnatcatcher, and not a Wren at all. She would be inclined to feel despondent, and to think that so far she was just not very sensitive to the kinds of features which distinguish birds from one another. The ostending ceremony would be empty, except insofar as it worked as a heuristic device for calling the bird's features to mind. And in that case, the ceremony itself, qua baptism, would drop out of the picture as irrelevant.
It might be thought that the ceremony might still have created some sort of concept. Perhaps the concept which covers all five birds is not one which ornithologists find useful, but it might be a genuine concept for all that. It is instructive to think about when such a claim would seem plausible. If this 'private linguist', presented with many birds, unerringly divided them into F and not-F birds, we might agree that there was a concept, but if the division was
done chaotically we would not even grant that she had a concept. But how would we decide the division was 'unerring'? Well, first, if we could give a public definition, even if the child couldn't articulate it, that would suffice. The House Wren, the Carolina Wren, the Bewick Wren, the Marsh Wren and the Gnatcatcher all, for example, have a throatless, turned-up-nose kind of look. A child who could distinguish those from the titmouse, the robin, and the
sparrow would have made quite a lot of progress. But in that case our acceptance of the
'private' concept as genuine rests on its conformity with a public concept. Second, if there was enough consistency to establish a practice which we could cotton on to, that too would suffice. But suppose, for example, the child were confidently to class a bird as F at one time, and when presented with the same, or what seemed to us to be an exactly similar bird she (again
confidently) were to claim it was not-F; meanwhile, when presented with, by any normal standards, two very different birds she unhesitatingly were to say they were both F. We might try different hypotheses to make sense of his concept: if she classed a Thrasher and a Shrike as F, say, we might wonder if the singing abilities of the bird, rather than their appearance were important. But that hypothesis could be dashed by the inclusion of a Grackle and the exclusion of the Lark. We would judge whether or not the child was making progress with her bird spotting by whether or not she had learned to make the same discriminations as ourselves (and the book). If the child could give no account of her 'concept', and we could not articulate one for her, and no matter how long the process went on we could never establish a practice to join in, we would not believe she had a genuine concept (supposing there is no joke here of the 'when is a raven like a writing desk?' variety). We would think she was making no progress at all.
And her mere confidence that she was right would be no guarantee at all that there was a genuine concept. As well as confidence we demand objective correction. When she suddenly realised on turning the page that the term House Wren was too narrow to fix her bird, her certainty that she had formed a concept was subject to objective constraints. What are the
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