"Come," he says, "answer me first, you Papists, where did the Scriptures enjoin baby-baptism, churching of women, marrying by priests, holy water to frighten the devil? Come now, you that are called Protestants, and first those who are called Episcopalians, where do the Scriptures own such persecutors, false prophets, tithemongers, deniers of revelations, opposers of perfection, men-pleasers, time-servers, unprofitable teachers?" The Separatists are similarly cudgeled: they are "groveling in beggarly elements, imitations, and shadows of heavenly things." Presently, a Presbyterian minister named Vincent attacked Quakerism. Joseph Besse, Penn's earliest biographer, says that Vincent was "transported with fiery zeal;" which, as he remarks in parenthesis, is "a thing fertile of ill language." Penn challenged him to a public debate; and, this not giving the Quaker champion an opportunity to say all that was in his mind, he wrote a pamphlet, called "The Sandy Foundation Shaken." The full title was much longer than this, in the manner of the time, and announced the author's purpose to refute three "generally believed and applauded doctrines: first, of one God, subsisting in three distinct and separate persons; second, of the impossibility of divine pardon without the making of a complete satisfaction; and third, of the justification of impure persons by an imputed righteousness." Penn's handling of the doctrine of the Trinity in this treatise gave much offense. He had taken the position of his fellow-religionists, that the learning of the schools was a hindrance to religion. He sought to divest the great statements of the creed from the subtleties of mediæval philosophy. He purposed to return to the Scripture itself, back of all councils and formulas. Asserting, accordingly, the being and unity of Father, Son, and Holy Ghost, he so refused all the conventional phrases of the theologians as to seem to them to reject the doctrine of the Trinity itself. He did deny "the trinity of distinct and separate persons in the unity of essence." If the word "person" has one meaning, Penn was right; if it has another meaning, he was wrong. If a "person" is an individual, then the assertion is that there are three Gods; but if the word signifies a distinction in the divine nature, then the unity of God remains. As so often happens in doctrinal contention, he and his critics used the same words with different definitions. The consequence was that the bishop of London had him put in prison. He was restrained for seven months in the Tower.