Dr. Wallis, the Savillian professor of Geometry, wrote a pamphlet[255] in defence of the doctrine of the Trinity, and employed some of the strangest expressions and illustrations with regard to the mystery that were ever conceived by any human being. “What is it,” he asks, “that is pretended to be impossible? ’Tis but this, that there be three _somewhats_, which are but one God, and these _somewhats_ are called Persons.” To explain the Trinity in unity, he compares the Almighty to a _cube_, with its length, breadth, and height infinitely extended. The length, breadth, and height of the cube, he says, are equal, and they are the equal sides of one substance--a fair resemblance of Father, Son, and Holy Ghost. This _longum_, _latum_, _profundum_, such are his words, is one cube of three dimensions, yet but one body; and this Father, Son, and Holy Ghost are three Persons, and yet one God. Vain attempts were made by the early Fathers to give definite conceptions of the mode of the Divine existence--the sun and its rays, a fountain and its streams, reason and speech, ointment and fragrance, being employed for the purpose; but Dr. Wallis attained to an originality as unenviable as it was startling; and were it not for his known candour and piety, it might be supposed he intended to turn the orthodox doctrine into ridicule. [Sidenote: 1693–8.] Dr. Sherlock, Dean of St. Paul’s and Master of the Temple, now in the black books of High Churchmen, undertook to meet the new attacks upon the Trinity; and, as so much was made of the assumed unreasonableness of that doctrine, he commenced his vindication of it with an elaborate argument to prove that it involves no contradiction whatever. He used the shield of reason to resist the darts of reason. His notion was, that self-consciousness constitutes the numerical unity of a Spiritual Being,--that the unity of a mind or spirit reaches as far as its self-consciousness,--that, in the three Persons of the Trinity, there is what may be called a mutual self-consciousness, a self-consciousness common to the three; and that therefore these three Persons are essentially and numerically one. A moral union in knowledge, will, and love, he says, is the only union of created spirits; but there is an essential union between Father, Son, and Holy Ghost, through the existence of a mutual consciousness. This notion contains, according to Sherlock, the true faith of a Trinity in unity. It is orthodoxy rationalized. It does not confound the Persons; it does not divide the substance.[256] After working out an abstruse argument to this effect, and after endeavouring to show there is authority in some of the Fathers for his theory, he concludes by taking up, _seriatim_, certain objections which had been urged in recent Unitarian writings. [Sidenote: THE TRINITY.]