in the that "theories supplied by reason should be verified by sensory data, aided by instruments, and corroborated by trustworthy witnesses" were (and still are) considered "one of the first important formulations of the scientific method on record". This idea that Bacon was a modern experimental scientist reflected two views of the period: that the principal form of scientific activity is experimentation and that 13th-century Europe still represented the "Dark Ages". This view, which is still reflected in some 21st-century popular science books, portrays Bacon as an advocate of modern experimental science who emerged as a solitary genius in an age hostile to his ideas. Based on Bacon's apocrypha, he is also portrayed as a visionary who predicted the invention of the submarine, aircraft, and automobile. Consistent with this view of Bacon as a man ahead of his time, H.G. Wells's Outline of History attributes this prescient passage to him:Machines for navigating are possible without rowers, so that great ships suited to river or ocean, guided by one man, may be borne with greater speed than if they were full of men. Likewise cars may be made so that without a draught animal they may be moved cum impetu inaestimabili, as we deem the scythed chariots to have been from which antiquity fought. And flying machines are possible, so that a man may sit in the middle turning some device by which artificial wings may beat the air in the manner of a flying bird. However, in the course of the 20th century, Husserl, Heidegger and others emphasised the importance to modern science of Cartesian and Galilean projections of mathematics over sensory perceptions of nature; Heidegger in particular noted the lack of such an understanding in Bacon's works. Although Crombie, Kuhn and continued to argue for Bacon's importance to the development of "qualitative" areas of modern science, Duhem, Thorndike, Carton and Koyré emphasised the essentially medieval nature of Bacon's . Research also established that Bacon was not as isolated—and probably not as persecuted—as was once thought. Many medieval sources of and influences on Bacon's scientific activity have been identified. In particular, Bacon often mentioned his debt to the work of Robert Grosseteste: his work on optics and the calendar followed Grosseteste's lead, as did his idea that inductively-derived conclusions should be submitted for verification through experimental testing. Bacon noted of William of Sherwood that "nobody was greater in philosophy than