Could there be a language only I can understand? A private diary of sensations, each sign fastened to its meaning by inward pointing alone? Then there would be no difference between my following the rule and my merely believing I follow it — and a rule I cannot fail to follow is no rule. Meaning needs a public, the way a handshake needs another hand. This is why the text before you is editable. A text only its author could correct would be a text without a language.