We must particularly observe here, that our Lord did not say, that we may be all one, but that they may be all one, as Thou, Father, in Me, and I in Thee, are one, understood. For the Father is so in the Son, that They are one, because They are of one substance; but we can be one in Them, but not with Them; because we and They are not of one substance. They are in us, and we in Them, so as that They are one in Their nature, we one in ours. They are in us, as God is in the temple; we in Them, as the creature is in its Creator. Wherefore He adds, in Us, to shew, that our being made one by charity, is to be attributed to the grace of God, not to ourselves.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: Tr. cx