It is significant that during the "age of faith" in Europe no philosopher of merit arose, and the only philosophy permitted was the puerile Scholastic-Aristotelic. This scholastic philosophy, hemmed in between metaphysics and theology, sought to reconcile Plato, Plotinus, and Aristotle with the needs of orthodoxy, and split hairs over subtle essences and entities. Francis Bacon impeaches, in this manner, the medieval philosophers: "Having sharp and strong wits, and abundance of leisure, and small variety of reading, but their wits being shut up in the cells of a few authors, as their persons were shut up in the cells of monasteries and colleges, and knowing little history, either of nature or time, did out of no great quantity of matter and infinite agitation of wit spin out unto us those laborious webs of learning which are extant in their books." The sole preoccupation of medieval philosophy seemed to be conjectures as to what would happen to man after death, and the entire system of thought was based on authority. The medieval philosopher turned in disdain from the arduous path of investigation of actual phenomena and confidently believed that he could find truth by easy reliance upon revelation and the elaboration of dogmas. A few brave minds rebelled against this unnatural imprisonment of the intellect, with the usual consequences. Peter Abelard was condemned for his scepticism at a council at Sens in 1140; the philosophy of John Scotus Erigena was condemned for its pantheistic ideas by a council at Sens in 1225; and the pantheistic views of Bruno had much to do with his martyrdom in the year 1600. Montaigne, the pioneer of modern scepticism, gave voice to his repugnance for dogmas in his brilliant Essays, in which he stated that all religious opinions are the result of custom; and that he doubted if, out of the immense number of religious opinions, there were any means of ascertaining which were accurate. Bacon, Hobbes, Locke, and Descartes were the inaugurators of a school of thought which is characterized by its practical spirit; and while these men professed theistic beliefs, their systems of thought had done much, when applied and amplified by their followers, to undermine that belief. These men furnished the source of a later agnosticism. Thomas Hobbes agreed with Bacon and Galileo that all knowledge starts from experience, and, carrying out the inductive method of Bacon, he produced his "Leviathan" in 1651. It was promptly attacked by the clergy of every country in Europe. Hobbes says of the immortality of the soul, "It is a belief grounded upon other men's sayings that they knew it supernaturally; or that they knew those who knew them, that knew others that knew it supernaturally."