social and philanthropic temperament retired into solitude to study those Laws in detail, and to impart their knowledge to a few chosen pupils. Many of them studied the Laws of mental development by the method of mathematical analysis. The vulgar called such students Wizards and other harsh names. The pursuit of mathematical Logic was often forbidden; the books of "Grammarye" were burned; and sometimes the writers and readers of them. At other times Wizards were held in high honour. Is it not possible that the famous breast-plate of Aaron, which was consulted in mental difficulties, may have had inscribed on it a selection of the Natural and Geometric Symbols of orderly mental sequence?
In modern times it has been assumed that the study of mathematical Logic must have been "mystical" or "fanciful." But in the middle of last century the Science was revived by a group of writers, among the foremost of whom may be mentioned Babbage, De Morgan, Gratry, and Boole. These philosophers have reclaimed us from bondage to the ignorant dictatorship of the opponents of "Grammarye," by proving that all the more important thought-processes can be illustrated Algebraically. Whatever can be stated in Algebraic symbols may legitimately be expressed, so far as possible, by mechanical action, or in diagrams. The practical possibilities of Algebraic notation are, it is true, far wider than those of mechanical or pictorial representation; but, when a truth has once been expressed Algebraically, it can no longer be considered fanciful to illustrate, by motion or by diagram, as much of it as is capable of such illustration. We are therefore free to teach the
