Luther himself, indirectly, invited his hearers to ask this question concerning his calling. “Whoever teaches anything new or strange” must be “called to the office of preacher” he frequently declares of those new doctrines which differed from his own; no one who has not a legitimate mission will be able to withstand the devil, but on the contrary will be cast down to hell.[431] Even in the case of the ordinary and regular office, Luther demands a legitimate mission; for the office of extraordinary messenger of God, he is still more severe. For here it is a question of the extraordinary preaching of truths previously unknown or universally forgotten or questioned, and of the reintroduction of doctrine. Here he rightly requires that whoever wishes to introduce anything new or to teach something different from the common, must be able to appeal to miracles in support of his vocation. If he is unable to do this, let him pack up and depart.[432] Elsewhere, as he correctly puts it: “Where God wills to alter the ordinary ways, He ever performs miracles.”[433] (Cp. vol. i., p. 225 f.) His teaching is, “There are two sorts of vocations to the office of preacher”; one takes place without any human means by God alone [the extraordinary call], the other [the ordinary] is effected by man as well as by God. The first is not to be credited unless attested by miracles such as were performed by Christ and His Apostles. Hence, if they come and say God has called them, that the Holy Ghost urges them, and they are forced to preach, let us ask them boldly: “What signs do you perform that we may believe you?”[434] (Mark xvi. 20). Logically enough Luther also demanded miracles of Carlstadt, Münzer and the Anabaptists. Which of the two kinds of vocation must we see in Luther’s case? Was his the ordinary one, which keeps to the well-trodden path, or the extraordinary one, which “strikes out a new way”? Simple as the question appears, it is nevertheless difficult to give a straight answer in Luther’s own words.