In 1709, when he was twenty-four years old, Berkeley presented himself to the world of empty verbal reasoners as the author of what he calls modestly _An Essay towards a New Theory of Vision_. It was dedicated to Sir John Percival, his correspondent afterwards for more than twenty years; but I have not discovered the origin of their friendship. The _Essay_ was a pioneer, meant to open the way for the disclosure of the Secret with which he was burdened, lest the world might be shocked by an abrupt disclosure. In this prelude he tries to make the reader recognise that in ordinary seeing we are always interpreting visual signs; so that we have daily presented to our eyes what is virtually an intelligible natural language; so that in all our intercourse with the visible world we are in intercourse with all-pervading active Intelligence. We are reading absent data of touch and of the other senses in the language of their visual signs. And the visual signs themselves, which are the immediate objects of sight, are necessarily dependent on sentient and percipient mind; whatever may be the case with the tangible realities which the visual data signify, a fact evident by our experience when we make use of a looking-glass. The material world, so far at least as it presents itself visibly, is _real_ only in being _realised_ by living and seeing beings. The mind-dependent _visual_ signs of which we are conscious are continually speaking to us of an invisible and distant world of _tangible_ realities; and through the natural connexion of the visual signs with their tactual meanings, we are able in seeing practically to perceive, not only what is distant in space, but also to anticipate the future. The Book of Vision is in literal truth a Book of Prophecy. The chief lesson of the tentative _Essay on Vision_ is thus summed up:—