This charge cannot be made against the two authors whose voices were raised in opposition to the prevailing opinions as to the appropriation of the sea before the work of Grotius appeared, and of whose writings he made considerable use. One of these was a Spanish monk, Francis Alphonso de Castro, who wrote about the middle of the sixteenth century, protesting against the Genoese and Venetians prohibiting other peoples from freely navigating the Ligurian and Adriatic Seas, as being contrary to the imperial law, the primitive right of mankind, and the law of nature; and also against the Spanish and Portuguese claims for exclusive rights to the navigation to the East and West Indies.[614] The other author, also a Spaniard, was Ferdinand Vasquez or Vasquius, who expressed the same opinions as de Castro, and for the same reasons. He held that the sea could not be appropriated, but had remained common to mankind since the beginning of the world; that the claim of the Portuguese to forbid to others the navigation to the East Indies, and that of the Spaniards to a similar prohibition to sail through “the spacious and immense sea” to the West Indies, were no less vain and foolish (_non minus insanæ_) than the pretensions of the Venetians and Genoese. The law of prescription, he said, was purely civil, and could have no force in controversies between princes and peoples who acknowledged no superior, because the peculiar civil laws of any country were of no more value with respect to foreign nations than as if they did not exist; to decide such controversies recourse must be had to the law of nations, primitive or secondary, which it was evident could never admit of such a usurpation of a title to the sea. With regard to the right of fishery, Vasquius drew a distinction between fishing in the sea and in rivers or lakes. He held that the sea had been from the first, and still remained, by the primitive right of mankind, free both for navigation and fishing, and that its use could not be exhausted by fishing, while lakes and rivers may be so exhausted.[615] From the foregoing, it will be seen that Grotius had ready to his hand many of the legal arguments of which he made so much use; but the strength of his work lay rather in its appeal to the sense of justice and the conscience of the free peoples of Christendom, to whom it was dedicated. The Spanish authors, moreover, were not in a position to assail the validity of the Papal Bulls, upon which the Spanish and Portuguese claims were partly founded, whereas it was against them that the Protestant writer levelled some of his most powerful philippics.