A few authorities maintained that such incomes had no justification. In the thirteenth century Henry of Ghent condemned the traffic in rent charges; in the sixteenth Dominicus Soto maintained that the returns to the silent partner in an enterprise ought not to exceed a fair equivalent for his risks; about the same time Pope Sixtus V denounced the triple contract as a form of usury. Nevertheless, the great majority of writers admitted that all these transactions were morally lawful, and the gains therefrom just. For a time these writers employed merely negative and _a pari_ arguments. Gains from rent charges, they pointed out, were essentially as licit as the net rent received by the owner of the land; and the interest received by a silent partner, even in a triple contract, had quite as sound a moral basis as rent charges. By the beginning of the seventeenth century the leading authorities were basing their defence of industrial interest on positive grounds. Lugo, Lessius, and Molina adduced the productivity of capital goods as a reason for allowing gains to the investor. Whether they regarded productivity as in itself a sufficient justification of interest, or merely as a necessary prerequisite to justification, cannot be determined with certainty. At present the majority of Catholic writers seem to think that a formal defence of interest on capital is unnecessary. Apparently they assume that interest is justified by the mere productivity of capital. However, this view has never been explicitly approved by the Church. While she permits and authorises interest, she does not define its precise moral basis.