A human lifespan is less than a thousand months long. You need to make some time to think how to live it.

The democracy of blogging and tweeting is absolutely terrific in one way. It is also the most effective producer of rubbish and insult and falsehood we have yet invented.

I am putting together a secular bible. My Genesis is when the apple falls on Newton's head.

I spent the first 13 years of my life in Zambia. In Africa you can't walk in the countryside and think. You might be eaten by a lion. You have to read instead.

My mother was a straight-up-and-down racist of a very marked kind. She used to laugh at the shopping lists the cook would try to copy out. It would never have occurred to her to teach him to read.

I would imagine Jesus was a kind of Jewish reformer. If you were looking for an equivalent to the figure you dimly perceive through the gospels it would probably be a Richard Dawkins.

I'm a vegetarian, but I wear leather shoes. Some people say that's a contradiction; I say I'm doing my best.

I used to be a terrible hypochondriac when I was young and a great reader of medical dictionaries. One day I realised that I was not actually frightened of terminal illness but of not getting done the things I wanted to get done.

I recently retraced on foot a famous journey that William Hazlitt made from Shropshire to Somerset to visit Wordsworth and Coleridge. I spent two weeks slogging through nettle beds before I realised the bastard had taken the coach.

When I was 14 a chaplain at school gave me a reading list. I read everything and I went back to him with a question: how can you really believe in this stuff?

I'm passionately in favour of legalising heroin and cocaine. But I despise people who depend on these things. If you really want a mind-altering experience, look at a tree.

I don't believe in killing animals, but I think President Obama did a justifiable thing in swatting a fly. Flies spread disease.

Christian churches and Muslim groups have no more right to have their say than women's institutes or trades unions. The government has actively encouraged faith-based education, and therefore given a megaphone to religious voices and fundamentalists.

I have enough faith in statistics to know there must be conscious life on other planets.

Initials can be useful to hide behind. I once heard Jonathan Ross on the radio asking Kirsty Young who she had coming up on Desert Island Discs. When she mentioned "AC Grayling" Ross replied: "Oh, I know her."

Science is the outcome of being prepared to live without certainty and therefore a mark of maturity. It embraces doubt and loose ends.

I'm not sure it is possible to think too much. You don't refresh your mind by partying in Ibiza.

Life is all about relationships. By all means sit cross-legged on top of a mountain occasionally. But don't do it for very long.

Every professor of philosophy needs a nine-year-old daughter. Mine has a habit of saying, "Daddy, that is a very silly idea." She is always right.

• Liberty in the Age of Terror, by AC Grayling, is published by Bloomsbury, £12.99