First - the sentence as presented is false.
Second - depending on how the sentence is meant in context, there may be truth contained in it. Jesus prayed for a very special unity among His followers.
20 "I do not pray for these only, but also for those who believe in me through their word, 21 that they may all be one; even as thou, Father, art in me, and I in thee, that they also may be in us, so that the world may believe that thou hast sent me. (John 17:20-21)
Jesus calls for us to be one even as He and the Father are one. To accomplish this in faith we seek to conform ourselves to Christ - to conform our wills to His Will - so that, as St Paul says, it is not we who live, but Christ who lives in us. (Gal 2:20) Such unity - such conformance can certainly be viewed as being of a single mind, a single soul but existing in separate bodies.
Yet - even though we are called to such unity, such perfection (Mt 5:48), there remains in us this thing called “free will”. This free will allows us to surrender to Christ, but it also allows us to deny him. We can give and we can take away. So ultimately, until we are perfected in Christ, we remain as separate and distinct souls. Souls for which we are accountable before God.
Peace
James