The Definition of a "Gentleman"

When I started out teaching English to adults here in France, I remember very well reminding my students when writing letters always to put their own address in the top right-hand corner (I think). But after 25 years in this racket followed by 15 years in which I found myself writing countless letters in French, I am no longer sure where to put my address. Not that it matters very much since no-one writes letters any more!


In the same vein, I have somewhere at the back of my mind a definition of what constitutes a "gentleman". "A gentleman", I recall, "is someone who never unwittingly gives offence". As with so many sayings and principles one learns at a young age, I never questioned the truth of this definition. But just recently I have begun to wonder whether I have remembered correctly. Does this mean that a gentleman is someone who sometimes wittingly or deliberately gives offence? Sounds more like Jonathan Ross to me.
Perhaps the definition is "someone who never wittingly gives offence", but in that case the gentleman stands revealed as a well-meaning dolt - not exactly the image we wish to promote. Could it be that the original expression was "someone who never willingly gives offence"? I really don't know.
There is actually another definition, supplied by Jonathan Miller in Beyond the Fringe. In old railway carriages, passengers visiting the toilets were greeted by the following definition: "Gentlemen lift the seat".
Here again, I don't suppose it matters very much as there are no gentlemen to be found nowadays, present company excepted of course.