On the holy spirit
It is as if a sort of communal personality came into existence. Of course, it is not a real person: it is only rather like a person. But that is just one of the differences between God and us. What grows out of the joint life of the Father and Son is a real Person, is in fact the Third of the three Persons who are God.
This third Person is called, in technical language, the Holy Ghost or the “spirit” of God. Do not be worried or surprised if you find it (or Him) rather vaguer or more shadowy in your mind than the other two. I think there is a reason why that must be so. In the Christian life you are not usually looking at Him: He is always acting through you. If you think of the Father as some- thing “out there,” in front of you, and of the Son as someone standing at your side, helping you to pray, trying to turn you into another son, then you have to think of the third Person as something inside you, or behind you. Perhaps some people might find it easier to begin with the third Person and work backwards. God is love, and that love works through men—especially through the whole community of Christians. But this spirit of love is, from all eternity, a love going on between the Father and Son.
Mere Christianity. Copyright © 1952, C. S. Lewis Pte. Ltd. Copyright renewed © 1980, C. S. Lewis Pte. Ltd. All rights reserved. Used with permission of HarperCollins Publishers. Words to Live By: A Guide for the Merely Christian. Copyright © 2007 by C. S. Lewis Pte. Ltd. All rights reserved. Used with permission of HarperCollins Publishers.