"The universal jargon, in the sense explained above, is the same for the child and for the adult. It is the same for a Robinson Crusoe as for a human society. If Robinson wants to join what is in a protocol of yesterday with what is in his protocol today, that is, if he wants to make use of language at all, he must make use of the ‘intersubjective’ language. The Robinson of yesterday and the Robinson of today stand precisely in the same relation in which Robinson stands to Friday."