Writers on public law have invented many ingenious theories to explain and justify, on rational grounds, so fundamental a difference between the two kinds of warfare. ‘To make prize of a merchant ship,’ says Dr. Whewell, ‘is an obvious way of showing (such a ship) that its own State is unable to protect it at sea, and thus is a mode of attacking the State;’[65] a reason that would equally justify the slaughter of nonagenarians. According to Hautefeuille, the differences flows naturally from the conditions of hostilities waged on different elements, and especially from the absence at sea of any fear of a rising _en masse_ which, as it may be the result of wholesale robbery on land, serves to some extent as a safeguard against it.[66] A simpler explanation may trace the difference to the maritime Piracy which for many centuries was the normal relation between the English and Continental coasts, and out of which the navies of Europe were gradually evolved. Sir H. Nicolas, describing the naval state of the thirteenth and early part of the fourteenth century, proves by abundant facts the following picture of it: ‘During a truce or peace ships were boarded, plundered, and captured by vessels of a friendly Power as if there had been actual war. Even English merchant ships were attacked and robbed as well in port as at sea by English vessels, and especially by those of the Cinque Ports, which seem to have been nests of robbers; and, judging from the numerous complaints, it would appear that a general system of piracy existed which no government was strong enough to restrain.’[67]