But he cannot err when he is *in cathedra *, that is, when he intends to make an instruction and decree for the guidance of the whole Church, when he means to confirm his brethren as supreme pastor, and to conduct them into the pastures of the faith. For then it is not so much man who determines, resolves, and defines as it is the Blessed Holy Spirit by man, which Spirit, according to the promise made by Our Lord to the Apostles, teaches all truth to the Church, and, as the Greek says and the Church seems to understand in a collect of Pentecost, conducts and directs his Church into all truth: *But when that Spirit of truth shall come, he will teach you all truth *or, will lead you into all truth (John xvi. 13). And how does the Holy Spirit lead the Church except by the ministry and office of preachers and pastors? But if the pastors have pastors they must also follow them, as all must follow him who is the supreme pastor, by whose ministry Our God wills to lead not only the lambs and little sheep, but the sheep and mothers of lambs; that is, not the people only but also the other pastors: he succeeds S. Peter, who received this charge: Feed my sheep. Thus it is that God leads his Church into the pastures of his Holy Word, and in the exposition of this he who seeks the truth under other leading loses it. The Holy Spirit is the leader of the Church, he leads it by its pastor, he therefore who follows not the pastor follows not the Holy Spirit.
But the great Cardinal of Toledo remarks most appositely on this place that it is not said *he shall carry the Church into all truth, *but he shall lead; to show that though the Holy Spirit enlightens the Church, he wills at the same that she should use the diligence which is required for keeping the true way, as the Apostles did, who, having to give an answer to an important question, debated, comparing the Holy Scriptures together; and when they had diligently done this they concluded by the: It hath seemed good to the Holy Spirit and to us; that is, the Holy Spirit has enlightened us and we have walked, he has guided us and we have followed him, up to this truth. The ordinary means must be employed to discover the truth, and yet in this must be acknowledged the drawing and presence of the Holy Spirit. Thus is the Christian flock led,-by the Holy Spirit but under the charge and guidance of its Pastor, who however does not walk at hazard, but according to necessity convokes the other pastors, either partially or universally, carefully regards the track of his predecessors, considers the *Urim *and *Thummim *of the Word of God, enters before his God by his prayers and invocations, and, having thus diligently sought out the true way, boldly puts himself on his voyage and courageously sets sail. Happy the man who follows him and puts himself under the discipline of his crook! Happy the man who embarks in his boat, for he shall feed on truth, and shall arrive at the port of holy doctrine !
Thus he never gives a general command to the whole Church in necessary things except with the assistance of the Holy Spirit, who, as he is not wanting in necessary things even to second causes, because he has established them, will not be more wanting to Christianity in what is necessary for its life and perfection. And how would the Church be one and holy, as the Scriptures and .Creeds describe her? -for if she followed a pastor, and the pastor erred, how would she be holy; if she followed him not, how would she be one? And what confusion would be seen in Christendom, while the one party should consider a law good the others bad, and while the sheep, instead of feeding and fattening in the pasture of Scripture and the Holy Word, should occupy themselves in controlling the decision of their superior?