Kant is an unlikely source of humour, one might suppose, given his, by
all accounts, reined-in, well-regulated way of life. On the other hand,
others report that he could be quite a wit and good company when out
convivially eating with others. Be that as it may, the connection with
Kant is not with him personally, but with that perhaps even more
unlikely joke-source, the Categorical Imperative.

Kant is an unlikely source of humour, one might suppose, given his, by
all accounts, reined-in, well-regulated way of life. 

It is not the Categorical Imperative that generates the joke, but rather it allows us to understand a kind of joke, and in such a way, in addition, that we may better understand the disquiet, even revulsion, some feel about that
kind of joke, especially if taken too far. But the title is justified,
and that it is Kant’s Joke,¹ as it is hard to see how the joke and
the misgivings we may have about such jokes can be understood properly
without understanding the central feature of Kant’s ethics. This is not
to say he would have liked the joke; he would not.

I refer of course to the so-called Practical Joke. Practical jokes
always involve some kind of deception, either by deliberate expressed
falsehood (one may say, lie) or by deliberate omission of some truth
that could be expressed. This deception may not be verbal, it may be
brought about by some action or inaction. Then, after some supposedly
suitable period of time the deception is reversed or at least the
initial situation revealed to be something other than it first seemed to
be.

Let’s take a couple of examples.

A friend’s exam results arrive, which you know mean a great deal to
them. You bowl up to them with the envelope, and open it, or ask them
whether you can open it (it doesn’t matter which) and solemnly declare
that they have failed, while knowing that they have passed. But then
after a suitable pause – how long that is depends on how much you want
to screw up the tension – you say ‘no you haven’t, you’ve passed!’

Here you boil some spaghetti, let it cool, and you put it in someone’s
bed down at the bottom where their feet go – perhaps you watch them get
into bed, though that’s not essential – the point being the alien shock
the person feels when they put their bare feet into what appears to be a
load of worms, or something else ghastly, that should not be there. The
relief comes, as it always does with practical jokes, on realising it is
only cold spaghetti.

Here you boil some spaghetti, let it cool, and you put it in someone’s bed down at the bottom where their feet go. 

In both cases, and in all cases in practical jokes, the trajectory of
the joke is the shock or an initial bad thing happening being replaced
by relief that things are not what they seem. Now for this not to be
simply cruel – for sometimes it is when practical jokes ‘go …

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