The joke is that all the prostitutes go on vacation when the philosophers come to town. The reason is that the other conventioneers do it, while philosophers just talk about it.
Although this sounds like a parody to Marx's notorious thesis on Feuerbach No.11, the truth here might be the old-fashion, naive ideology cliché: While philosophers keep doing it over and over for whatever reason, they tend to invent ever obscure theories to cover it up.
However, as you probably know, the new version of ideology goes like this: philosophers would lose the ability of doing it if they don't have some theories to talk about.
Or, maybe they are just trying to escape from the overwhelming desire or fear of doing it by keep talking?
Maybe. But there is still an alternative which is far more straightforward: they do gain more pleasures, or, as economists said, utilities, from talking than doing it.
Unfortunately, the alternative is unverifiable as well.
Fortunately, we have MRI now. All we need to do is to get some philosophers, put them on the machine and check their brains to see where in the brain the activity imposes and whether the talk makes it stronger...
