John 17:21

21. May be one Amid every diversity there is among true Christians a true unity. So amid many varieties, external and striking, the human race has a unity internal and absolute. One touch of feeling makes the whole world akin. Universal man, and man alone, has the moral emotion, the religious susceptibility, the power to possess an idea of the infinite God.

The European, the Chinaman, the Hottentot, can be brought to worship the Omnipotent; but not the dog, the elephant, or the gorilla. So, amid every outward diversity, there is in the Christian body the true unity of the Spirit. The attempt has been made to bring that body under one human head, the Pope, and what has been the result? The head became ambitious, corrupt, despotic, infidel, and bloody. This was substituting for God’s unity of the Spirit man’s unity of temporal power.

As thou… and I The opposer of the doctrine of the Trinity very vainly attempts to prove that the Logos, or Word, can be no more one with God, than one Christian man can be one with another. But the as here indicates not equality in degree, but similarity in nature according to the human likeness and proportion to the Divine. As of Christian perfection the ideal is God, so of Christian unity the model is the ever-blessed Trinity. (See note on Matthew 5:48. Also, John 14:9-10.) For man was made in the image of God. Of the Church, as of the Trinity, the unity is spiritual.

That… that… that There are three thats in this verse. The first two are parallel to each other, the latter enlarging the other, and both depend on pray in the previous verse. Christ directly prays that his followers may be one; and that they may be one in us. The third that depends upon these two. May they be one in us, that the world may be inspired, by that unity, with faith.

The world Stands in a double aspect: as the embodied enemy of Christ, and, as such, no object of prayer; and as the raw material from which the future Church must be won and shaped, and, as such, the object of this extension of prayer. And in the following verses Christ prays that the Church may be perfect in one, both for its own blessed sake and for the winning the world to faith. No limits are assigned to the diffusion of faith through the world; but the Saviour, justifying a holy ambition in his Church to win the whole, prays that the world may believe, and nothing less.