The first is in two parts: in the first, he shows what a sacrament is; in the second, the necessity of the institution of the sacraments, at: The sacraments were instituted for a threefold cause.
Prima in duas: in prima ostendit quid est sacramentum; in secunda necessitatem institutionis sacramentorum, ibi, triplici autem ex causa sacramenta instituta sunt.