Throughout the twelfth century there were many signs that the European intelligence was recovering courage and leisure, and preparing to take up again the intellectual enterprises of the first Greek scientific enquiries and such speculations as those of the Italian Lucretius. The causes of this revival were many and complex. The suppression of private war, the higher standards of comfort and security that followed the crusades, and the stimulation of men’s minds by the experiences of these expeditions were no doubt necessary preliminary conditions. Trade was reviving; cities were recovering ease and safety; the standard of education was arising in the church and spreading among laymen. The thirteenth and fourteenth centuries were a period of growing, independent or quasi-independent cities; Venice, Florence, Genoa, Lisbon, Paris, Bruges, London, Antwerp, Hamburg, Nuremberg, Novgorod, Wisby and Bergen for example. They were all trading cities with many travellers, and where men trade and travel they talk and think. The polemics of the Popes and princes, the conspicuous savagery and wickedness of the persecution of heretics, were exciting men to doubt the authority of the church and question and discuss fundamental things. We have seen how the Arabs were the means of restoring Aristotle to Europe, and how such a prince as Frederick II acted as a channel through which Arabic philosophy and science played upon the renascent European mind. Still more influential in the stirring up of men’s ideas were the Jews. Their very existence was a note of interrogation to the claims of the church. And finally the secret, fascinating enquiries of the alchemists were spreading far and wide and setting men to the petty, furtive and yet fruitful resumption of experimental science. And the stir in men’s minds was by no means confined now to the independent and well educated. The mind of the common man was awake in the world as it had never been before in all the experience of mankind. In spite of priest and persecution, Christianity does seem to have carried a mental ferment wherever its teaching reached. It established a direct relation between the conscience of the individual man and the God of Righteousness, so that now if need arose he had the courage to form his own judgment upon prince or prelate or creed. As early as the eleventh century philosophical discussion had begun again in Europe, and there were great and growing universities at Paris, Oxford, Bologna and other centres. There medieval “schoolmen” took up again and thrashed out a series of questions upon the value and meaning of words that were a necessary preliminary to clear thinking in the scientific age that was to follow. And standing by himself because of his distinctive genius was Roger Bacon (circa 1210 to circa 1293), a Franciscan of Oxford, the father of modern experimental science. His name deserves a prominence in our history second only to that of Aristotle.