At length, through Lord Percival, Berkeley learned that Walpole would not allow the parliamentary grant of, L20,000 for the Bermuda College, and returned to England at the close of 1732.  His Whitehall estate he conveyed to Yale College for the maintenance of certain scholarships.  From England he sent over nearly a thousand volumes for the Yale library, the best collection of books ever brought at one time to America, being helped in the undertaking by some of the Bermuda subscribers.  A little later he sent a collection of books to Harvard College also, and presented a valuable organ to Trinity Church in Newport.

Shortly after his return, Berkeley was appointed Bishop of Cloyne, near Cork in Ireland, and here he remained for about eighteen years.  Although a recluse, he wrote much, and he kept up his loving relations with old friends who still survived.  He had several children to educate, and he cultivated music and painting.  He attempted to establish manufactures, and to cultivate habits of industry and refinement among the people.  The winter of 1739 was bitterly cold.  This was followed by general want, famine, and disease.  Berkeley and his family lived simply and gave away what they could save.  Large numbers of the people died from an epidemic.  In America Berkeley’s attention had been drawn to the medicinal virtues of tar, and he experimented successfully with tar-water as a remedy.  Becoming more and more convinced of its value, he exploited his supposed discovery with his usual ardor, writing letters and essays, and at length ’A Chain of Philosophical Reflections and Enquiries concerning the Virtues of Tar-water and divers other subjects connected together and arising one from another.’  This was called ‘Siris’ in a second edition which was soon demanded.  Beginning with the use of tar-water as a remedy, the treatise gradually developed into the treatment of the largest themes, and offered the ripest fruits of the Bishop’s philosophy.

Berkeley’s system was neither consistent nor complete, but much of it remains sound.  In brief, he contended that matter has no independent existence, but is an idea in the supreme mind, which is realized in various forms by the human mind.  Without mind nothing exists.  Cause cannot exist except as it rests in mind and will.  All so-called physical causes are merely cases of constant sequence of phenomena.  Far from denying the reality of phenomena, Berkeley insists upon it; but contends that reality depends upon the supremacy of mind.  Abstract matter does not and cannot exist.  The mind can only perceive qualities of objects, and infers the existence of the objects from them; or as a modern writer tersely puts it, “The only thing certain is mind.  Matter is a doubtful and uncertain inference of the human intellect.”

The essay upon Tar-water attracted great attention.  The good bishop wrote much also for periodicals, mainly upon practical themes; and in The Querist, an intermittent journal, considered many matters of ethical and political importance to the country.  Though a bishop of the Established Church, he lived upon the most friendly terms with his Roman Catholic neighbors, and his labors were highly appreciated by them.