Given the oh-so-serious mood of commentary and analysis, it's easy to forget: every good thinker must know how to laugh.
At breakfast this morning, my wife told my son an anecdote. When he was an infant, we put him in a wooden playpen. The idea was simple: stop him from crawling, climbing and generally destroying the joint. He looked at this new toy, lifted up the playpen and crawled out.
Hearing this at the table as he munched his banana toast, my son cracked into laughter. His eyes wet and half-shut, his little white teeth showing, he chortled and snorted uncontrollably and unselfconsciously for a few minutes. As did his parents.
At what were we laughing? Most obviously, the reversal of expectations: the pen for confined play becomes itself the plaything, and in this frees its prisoner. We were laughing at the absurdity of it, in which parental plans were overturned by infant curiosity and play.
There is something very knowing in this laughter; something profoundly human. It is not spiteful mockery, though this too is part of what we are. It is, instead, a recognition of our imperfection: how easily and quickly our commonsense ideas and acts are undone by the world, including its babies. It is the buoyant equivalent of a sigh or shrug: a gesture at how rudely great and darkly wise we are.
Philosopher Alfred North Whitehead, a reverent man if not a mainstream Christian, once remarked that he was suspicious of religious people with no sense of humour. In his book Science and the Modern World he elaborated: ''Is it that nothing, no experience good or bad, no belief, no cause, is, in itself, momentous enough to monopolise the whole of life to the exclusion of laughter? Laughter is our reminder that our theories are an attempt to make existence intelligible, but necessarily only an attempt, and does not the irrational, the instinctive burst in to keep the balance true by laughter?''
His point was not that we can laugh at every grief; that we ought to trivialise others' misery. Instead, Whitehead was noting something vitally important for anyone who reflects, and behaves thoughtfully: there is always more than we know, and more than we are. It is an expression of scepticism, fallibility and finitude: the recognition that we are limited, situated creatures.
I'm not suggesting that my son, aged seven, is knowingly formulating an account of human imperfection, and the variety of absolute claims. (All in good time.) I'm suggesting that his laughter is a familiar response to upturned expectations, and is rooted in the fundamental gap between our minds and a baffling world.
That the cosmos is inexplicable and often unpredictable is not an excuse for giving up - laughter is not the first step to cynical apathy. It is not funny to simply stop trying to make sense of the world - this is just plain sad.
We laugh when we try but fail, because laughter is the only rational response to an unreasonable existence - without earnest struggle, there's nothing to laugh about.
This, in turn, means that laughter can be a sign of strength, not weakness. To shake one's head and snort at the vanity of one's achievements or aspirations is testament to one's willingness to keep on. Laughter, as the philosopher Nietzsche recognised in his book The Gay Science, is not for the weak: the deluded, the envious, the petty. It is for those brave enough to chortle at their own rightful attempts to live well and wisely in an absurd world.
I don't pretend that all of this was running through my head at breakfast, or that every gag is a philosophical axiom. I am simply arguing that good thought requires a good portion of humour. Just remember, as the Monty Python chaps put it, the last laugh is on you.
Dr Damon Young is a philosopher and author. His next book, Philosophy in the Garden, will be published next month.
