My pointing something out to you is a request for joint visual attention to the same object. It is based on a highly explicit general sense of the kind of creature you are: unlike other creatures, (most) humans have an unequivocal sense that others have minds. On top of this, there is a specific sense of your knowledge being defective compared with mine, based on my observation of your (literal) point of view. We are reminded just how remarkable this is when we encounter human beings who lack this sense: people with autism who have no integrated sense of themselves, and no sense of other's sense of themselves. A poignant early sign of autism is the failure to point – a gesture which usually appears towards the end of the first year of life, before the emergence of language. Pointing, in short, is a potent testimony to the infant's sense (again unique to human beings) of living in a shared, common world, a public reality, and of its communicative urge.

Pointing is pre-linguistic, but it is important not to exaggerate the sense in which it is proto-linguistic. Individual words belong to systems of signs and make sense only as part of such systems – as loci in semantic fields stitched together by grammar. By contrast, the field of pointing is the visual field, and its grammar is almost non-existent. St Augustine's notion that parents teach their children to speak by pointing at objects and uttering their names was brilliantly criticised by Wittgenstein in the opening pages of Philosophical Investigations, and led to some of his most famous theories about language. Reflecting on the modest role played by pointing as a bridge from babbling to speech awakens one's sense of the mysterious nature of language. Investigating the scope and limits of ostensive definition – defining words by literally pointing out their objects (eg "That's 'vermilion'") – casts an interesting light on the nature of linguistic reference, of universals, and of the very complex relationship between the arrays of material objects that surround us and the world as it is captured in spoken and written discourse.