What you mean by a good player is a man whose eye and muscles and nerves have been so trained by making innumerable good shots that they can now be relied on. They have a certain tone or quality which is there even when he is not playing, just as a mathematician’s mind has a certain habit and outlook which is there even when he is not doing mathematics.
 C. S. Lewis, Mere Christianity (1952). copy citation

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Author C. S. Lewis
Source Mere Christianity
Topic quality mind
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

“There is one further point about the virtues that ought to be noticed. There is a difference between doing some particular just or temperate action and being a just or temperate man. Someone who is not a good tennis player may now and then make a good shot. What you mean by a good player is a man whose eye and muscles and nerves have been so trained by making innumerable good shots that they can now be relied on. They have a certain tone or quality which is there even when he is not playing, just as a mathematician’s mind has a certain habit and outlook which is there even when he is not doing mathematics. In the same way a man who perseveres in doing just actions gets in the end a certain quality of character. Now it is that quality rather than the particular actions which we mean when we talk of a ‘virtue’.” source