So deep in the junction of the divine and human natures in our Lord's adorable Person lies the root of unity for that humanity which He purchased with His blood. It is in virtue of this headship that the whole mystical body is one, and "we all members one of another." By this headship our Lord nourishes and cherishes the Church, and communicates to her incessantly that stream of grace by which she lives. And as this headship flows from the union of the Godhead and Manhood, so it is inseparable from His Person, and incommunicable. But He has Himself, in His parting discourse, recorded by S. John, dwelt upon the great sacrament of unity, the result of this headship, and set it forth as the sign and seal of His own divine mission, and the one convincing proof of His religion's superhuman origin. By following His words we shall see that this unity is not simple but fourfold, and we shall trace the mutual relation and subordination to the divine Headship of its several kinds. 1. And first, "In[17] that day," says He, that is, after His own resurrection, "ye shall know that I am in My Father, and you in Me, and I in you," whereby He declares that, in the completion of the dispensation, the union between Himself and the faithful shall be such as to image out the mutual indwelling of the Father and the Son. Which again is further expressed, "I[18] am the true vine, and My Father is the husbandman. Every branch in Me that beareth not fruit He will take away: and every one that beareth fruit, He will purge it, that it may bring forth more fruit.... I am the vine; you the branches: he that abideth in Me, and I in him, the same beareth much fruit: for without Me you can do nothing. If any one abide not in Me, he shall be cast forth as a branch, and shall wither, and they shall gather him up and cast him into the fire, and he burneth. If you abide in Me, and My words abide in you, you shall ask whatever you will, and it shall be done unto you." In these words He sets forth that union of mystical influx, by cooperation with which His disciples keep His words and abide in His love, and of which He is Himself the immediate principle.