John 17:21 that they may all be one; even as You, Father, are in Me and I in You, that they also may be in Us, so that the world may believe that You sent Me.
John 17:22 “The glory which You have given Me I have given to them, that they may be one, just as We are one;
John 17:23 I in them and You in Me, that they may be perfected in unity, so that the world may know that You sent Me, and loved them, even as You have loved Me.
Again:-In John xvii. 9, Jesus says, in addressing hie Father–“I pray for them; I pray not for the world, but for them which thou hast given me.” But in the 2lst verse, it has been alleged by Arminians he does pray for the world:–in expressing his desire for the union of his people, he says–“that they all may be one, as thou, Father, art in me, and I in thee, that they also may be one in us,–that the world may believe that thou hast sent me.” Now, without considering at present the design of Arminians in this, I wish the reader to observe, what some Calvinists have said in reply. They have actually understood “the world ” in this last occurrence of it to mean the elect–God’s chosen people scattered throughout all nations, and the prayer as a petition that they might, all of them, in successive generations, be brought to the knowledge and faith of his name. In this way, it is alleged, the two verses are at once reconciled. And so, undoubtedly, they are; but the reconciliation, as it appears to me, is effected at the expense of every principle of fair and rational criticism; by making the same term signify, first one thing, repeatedly, and in direct and specified discrimination from another,–and then, all at once, and without warning, the very thing from which it had been distinguished; and that, not only in remote parts of the same prayer, but in the, very same sentence. In verses 9, 14, 16, 18, 21,23, 25, the world is used in express distinction from the chosen people of God; and the distinction is absolutely marked in the very verse in which it is supposed to signify that chosen people–”that thy also may be one in us that the world may believe that thou has sent me.” So that this extraordinary principle of interpretation makes those whose union was to be the means of conviction, and the world who were to be convinced by it, one and the same! This will never do. Nor is them the least occasion for having recourse to any process so anomalous. The principle of interpretation is simple. In the explanation just given, it is assumed that the phrase “that the world may believe” can mean nothing lees than that those signified by “the world,” whosoever they were, should all individually be brought to true and saving faith. But the prayer is for the unity of his disciples: and, things being spoken of according to their proper tendencies, this unity is sought, as an evidence to the world of his divine mission. This is all. The tendency of all evidence is to produce conviction. And in all cases, the general design of every one by whom evidence is presented, must be the same. It must correspond with the tendency. It must be to convince. Such is the tendency, and such we are warranted to consider the design, of all the evidence of this gospel, or of the mission of Christ, and the truth of his doctrines. The petition under consideration is framed, in its expression, upon this simple principle; meaning no more than that in the love and union of his disciples the world might have evidence of the truth, such a should tend, like all evidence, whether the effect actually resulted or not, to the production of faith–to the conviction of his having come from God.–And this is not the only text, to the explanation of which this simple principle, of things being spoken of according to their general tendency, is the key.
Ralph Wardlaw, Two Essays: I. On The Assurance of Faith: II. On The Extent of the Atonement, And Universal Pardon (Glasgow: Printed at the University Press, for Archibald Fullarton & Co., 1831), 280-283.