But when uttered by a Conservative politician, a head-master, or a Telegraph columnist, however, it becomes something different. It mutates into, "for a healthy mind, you need a healthy body". And its implication is that unless youngsters, in particular, engage in vigorous sporting activity, then their swotting and enervated book-learning will only make for pale features, clammy hands and early death. Just look at that Thomas Chatterton, for instance. Bet he never scored a try in his life.
It isn't very surprising that our current Prime Minister should hold this view. "The best days of my life at school", he said recently, "were the days when we had one form of cricket, or soccer, or rugger".
So he struck out with the bat, rucked in the loose, got nearly no academic qualifications and look at him now. This week, with what is being called Britain's-worst-medals-performance-since-Helsinki-in-1952, he has renewed his call for a greater emphasis on sports. His credo? "I believe that we in this country have devalued sport for too long."
At which point I invite the reader to take an extra hard look around today. Walk through a park, switch on the television, examine the bookshelves of friends, listen to male conversations in the pub. Would you say that we "undervalue sport"?
Hardly. Our lives are dominated by it. You can find all four terrestrial TV channels showing one sport or another simultaneously. Many educated people of my acquaintance will spend time and treasure on tennis, squash and golf, while lamenting the lack of hours available for reading, or music, or drama. The lack of PE teachers is regarded as a national scandal, just as the teaching of music slowly but silently slips out of the state education system. Boys who cannot read properly, and ought to be receiving additional help, are playing soccer after school five days a week.
The result is that we are - for all the hand-wringing and talk of "Academies of Sport" - a nation of sportsmen and women. But we are a nation of stupid sportsmen and women - badly read and with poor cultural resources - and that's why we lose. Our bodies are competitive, but our minds are not up to it.
When the German soccer star Jurgen Klinsmann came to Britain two years ago (for one fifteenth of the Shearer fee), he soon became the best striker in the country. Was it because he was faster, more skilful, more athletic than the Brits? No, he was just much brighter. Already fluent in Italian and French, within three months he spoke better English than most of his English team-mates. This is not a joke. The same goes for Eric Cantona - another who stands out. These players read books, watch films, hold real conversations. They know about people and psychology, understand the dynamics of teams, go out on the pitch and, as a result of their intellectual superiority, they play better.
In Euro 96 England were held by a German team that was less skilful than they, certainly no more committed, and missing several key players. But the Germans were cleverer - pacing themselves better, making the most out of their opponents' weaknesses. Only yesterday the British women's hockey team lost out to the Dutch in a penalty shoot-out. The British captain didn't appear to notice that the Dutch goalie saved everything placed to her right and let in all the shots on the left. Naturally, she pucked off to the goalie's right.
And it wasn't Linford Christie's running ability that cost him the 100 metres, was it? Mens sana in corpore sano. In the end, it's intellect that triumphs.