In the sixteenth century came the great revolt against the time-honoured authority of the Church, which effectively prepared the way for the marvellous development of Rationalism in the last three centuries. The reformers, indeed, extended little patronage to the exercise of reason in religious matters; they denounced it and its fruit, philosophical speculation, as an evil not to be tolerated; and Luther went so far as to assert (even to the disgust of the Church of Rome) that a proposition may be true in theology and false in philosophy. Still, by the force of their own example, they inevitably introduced the Rationalistic spirit, the right of personal speculation on authoritative teaching: when the impressiveness of their usurped authority waned, the practical lesson of their revolt, the right to examine and criticise, was more clearly perceived. At the same time, no adequate and permanent authority was established in place of the rejected papacy; an admittedly fallible authority only encourages criticism and individual speculation. The iron bond of unity and discipline was broken, never to be replaced; no authority remained that could absolutely enforce a devised formula, and against which revolt would have a supernatural demerit. A Church teaching in virtue of its collective wisdom, and expounding an obscure objective code of faith and morals, could never hope to repress individual vagaries.
Other causes co-operated happily in hastening the dawn of perfect liberty of thought. The rapid multiplication of sects and dissipation of spiritual jurisdiction made it possible for independent thinkers to escape a persecuting authority and take up a bold, isolated position. Culture, too, began to pass more extensively into the ranks of the laity, who were naturally more ready to express their scepticism than the professional theological caste. Secular sciences, history, and physics began to breathe freely at last and develop in utter disregard of religious doctrines. Printing was introduced; a religious controversy thus obtained an infinitely wider audience than it had had formerly, and the writings of sceptics were universally diffused. The destruction of a venerable authority, the violent changes of theological schemes, the deafening roar of controversy, the accumulation of diverse and contradictory opinions, tended to produce distrust in the educated and bewilderment in the uneducated. Such, briefly, were the predisposing conditions of modern Rationalism.
One important Rationalistic school, Socinianism, the revival of Arianism, and predecessor of modern Unitarianism, dates from the time of the Reformation itself. Still, it is only attributable to the Reformation in the sense that that movement afforded it some liberty of utterance and expansion. It may easily be traced through the Italian-Greeks of the Renaissance to the earlier Greek heresy; if, indeed, it may not be said to voice the unceasing impatience of the mind in all ages under the Christian mysteries, especially the dogma of the Trinity. This time, however, the system came to stay, and it has played a most important part in the rationalization of theology. But the broader Rationalistic movement soon began in earnest with the appearance of isolated writers of great authority, of enduring influence, and often of the most destructive scepticism. In 1588 Montaigne published the first great sceptical work of a thoroughly Pyrrhonist character. A literary critic of profound influence, he was in effect a Rationalist of the most advanced type; his essays were the inauguration of the modern period of Freethought. He was warmly supported by Charron, a French priest, and is even said to have profoundly influenced Pascal. Descartes also, with his system of philosophic doubt, assisted the growth of freedom and reflection. Bayle was not only profoundly sceptical in the composition of his Dictionary, but he made a most eloquent and effective appeal in smaller works, as the Compelle Intrare, for liberty of thought and expression. Even the religious Leibnitz earned the title of "Glöbenichts" (believer of nothing). Spinoza was profoundly destructive.
In England a series of powerful writers embodied the Rationalistic spirit with great effect in the seventeenth and eighteenth centuries. Bacon had virtually commenced the movement with his protest against "idols" and authority and the insistence on an empirical method. Hobbes followed with a most uncompromising iconoclasm. Locke introduced the empiric philosophy, which is so largely responsible for the Agnosticism of the nineteenth century. Hume developed the system and indicated its true conclusion, and diffused a literary scepticism with far-reaching effect. Gibbon brought the Rationalistic spirit to bear on history. If it is true that "the controversialists of successive ages are the puppets and unconscious exponents of the deep under-currents of their time," the Rationalistic spirit must have made rapid progress in England since the rejection of Papal despotism. One salutary effect of the controversies and of the downfall of Rome was the birth of a spirit of toleration for the first time in the history of Christianity; even orthodox writers, such as Chillingworth (the first to do so), began to teach "the absolute innocence of error."
In the course of the eighteenth century the controversy assumed a different character. Rationalistic criticism passed from the contents of Christianity to its external defences; the spirit was penetrating deeper every century. There was, it is true, a fierce revival of the Trinitarian controversy. The Unitarians waxed bolder and stronger in their attempt to rationalize theology, and some of their Trinitarian opponents, headed by Bull and Waterland, developed a semi-Rationalism on their own side, dropping off, as in the ancient controversy, into semi-Arianism on the one side, and Tritheism on the other. But the struggle is principally characterized by the rise of the Deistic school. Allied with the Voltairean school, which was permeating France with Rationalism, there was in England a powerful body of writers—Toland, Collins (the first to bear the title of Freethinker), Chubb, Woolston, Tindal, Shaftesbury, and Bolingbroke, who made a virulent organized attack upon the very credentials of Christianity, ridiculing its history and its mysterious contents, and denying the very possibility of miracles. They were opposed by Dr. S. Clarke, Dr. Berkeley, and Dr. Butler (the first two again developing a certain amount of private Rationalism in the course of their apologetic efforts). The rise and spread of Wesleyanism created a diversion in favour of the Rationalists by slighting the efforts of the evidential school and creating an emotional concentration upon the Atonement and similar doctrines. The fall of High-Churchism and the ascendancy of the Broad Church tended to produce a similar effect. Still, it is not too much to say that the Deistic controversy remains buried in the eighteenth century. As a consecration and development of the Rationalistic spirit, the Deistic school wrought an enduring effect. But even the brilliant writings of Bolingbroke and Shaftesbury are now practically shelved. Hume and Gibbon are the only Rationalists whose works pass on into the nineteenth century.
Such had been the progress of the Rationalistic spirit up to the period with which this sketch will deal. As a spirit, or method, it had been extensively used against orthodox belief; but few of its results were useful in the great struggle of the present century. The controversy once more changes its entire character, though animated by the same spirit. Modern Rationalism differs in two ways from Voltairean or Deistic Rationalism. It is more fundamental, and it is not merely destructive, but teaches also elevated social and ethical ideals to humanity. Once the spirit of criticism had successfully attacked the evidences of supernatural religion, it turned its attention to the evidences of natural religion, or pure Theism, which the older Rationalists had respected. The century opens with a development of the empirical philosophy which rapidly produces its most negative results. Coleridge introduces the transcendental philosophy from Germany, which he has learned from Kant's followers, and the first efforts of Biblical criticism from Lessing and Semler. In the course of the century the empirical philosophy developes into pure Agnosticism and Positivism, evokes a brilliant series of exponents from James Mill to Spencer, and obtains a wide acceptance from the gradually-educated country. German philosophy runs its course into Hegelian Pantheism, and its moral anxiety, in virtue of which it still clung to Theism, finds