The essential unity of the religious life is consistent with a great variety which is one of the glories of the Church, and permits a larger number of men to find a religious profession adapted to their needs and dispositions, and multiplies the services which religious render to Christian society and mankind in general. Besides the common end of religious life, which makes it a school of perfection, the different orders have special objects of their own, which divide them into contemplative, active, and mixed orders. The contemplative orders devote themselves to union with God in a life of solitude and retirement; the active orders expend their energy in doing good to men. If their activity is spiritual in its objects and requires contemplation for its attainment, they are mixed orders; such as those which are devoted to preaching and higher education. The orders keep the name of active order if they devote themselves to corporal works of mercy, such as the care of sick persons and orphans. The dominant note of their mode of life gives us, as we have seen, clerical, monastic, mendicant, military, and hospitaller orders. The vows divide them into orders with simple vows and solemn vows: even the number of vows differs in different institutes. There remain still two other points of difference which require to be considered, namely the juridical condition, which distinguishes religious orders from congregations, and the rule.