Once a man is united to God, how could he not live forever? Once a man is separated from God, what can he do but wither and die?
 C. S. Lewis, Mere Christianity (1952). copy citation

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Author C. S. Lewis
Source Mere Christianity
Topic God living
Date 1952
Language English
Reference
Note Adapted from a series of BBC radio talks made between 1942 and 1944
Weblink https://www.dacc.edu/assets/pdfs/PCM/merechristianitylewis.pdf

Context

“They are not a sort of prize which God could, if He chose, just hand out to anyone. They are a great fountain of energy and beauty spurting up at the very centre of reality. If you are close to it, the spray will wet you: if you are not, you will remain dry. Once a man is united to God, how could he not live forever? Once a man is separated from God, what can he do but wither and die? But how is he to be united to God? How is it possible for us to be taken into the three-Personal life?
You remember what I said in Chapter I about begetting and making. We are not begotten by God, we are only made by Him: in our natural state we are not sons of God, only (so to speak) statues.” source