It drives home the point that adopting a realistic approach towards the world does not consist in always reaching for a well-worn toolkit of timeless verities, nor does it consist in affecting a hard-boiled attitude so as to inoculate oneself forever against liberal enthusiasm. Realism, taken seriously, entails a never-ending cognitive and emotional challenge. It involves a minute-by-minute struggle to understand a complex and constantly evolving world, in which we are ourselves immersed, a world that we can, to a degree, influence and change, but which constantly challenges our categories and the definitions of our interests. And in that struggle for realism – the never-ending task of sensibly defining interests and pursuing them as best we can – to resort to war, by any side, should be acknowledged for what it is. It should not be normalised as the logical and obvious reaction to given circumstances, but recognised as a radical and perilous act, fraught with moral consequences. Any thinker or politician too callous or shallow to face that stark reality, should be judged accordingly.

My old friend and mentor Pío Baroja – who did not receive the Nobel Prize because the bright light of success does not always fall on the righteous – had a clock on his wall. Around the face of that clock there were words of enlightenment, a saying that made you tremble as the hands of the clock moved round. It said “Each hour wounds; the last hour kills”.

[O]ne of the great roof walkers of the world… talks about vertigo as a beast that has to be tamed piece by piece, that can never be overcome all at once.

Vertigo, he says, is not the fear that you will fall. It is the fear that you will jump. That, of course, is the thing that, when you are roof walking, you are taming. You are trying to unmoor your sense of danger and of not being able to trust yourself not to jump from your sense of beauty and the vision of a city that you get up high.

I roof-walk for very practical reasons: to see views that would otherwise be not really available to me in an increasingly privatized City of London.

The decent thing to do is to try as much as possible to avoid piquing their self-esteem. It's impolite to start an email with the main topic you want to discuss, and when I feel the need for a buffer, I generally talk about the weather or current events. I do not add subjective views when I do that - I don't say it's depressing because of the continual rain or the freezing cold. I make it a rule to write only the facts. I might say I'm writing this email in a room where it's starting to get warmer after the rain and ask how the recipient is doing, that the clock has just struck noon or there is a full moon in the sky. None of these words have much meaning to them, but they're only greetings. I think it's nice to avoid stimulating the recipient needlessly at the beginning of an email.

To see a World in a Grain of Sand
And a Heaven in a Wild Flower
Hold Infinity in the palm of your hand
And Eternity in an hour