Becoming a vegetarian is not merely a symbolic gesture. Nor is it an attempt to isolate oneself from the ugly realities of the world, to keep oneself pure and so without responsibility for the cruelty and carnage all around. Becoming a vegetarian is a highly practical and effective step one can take toward ending both the killing of nonhuman animals and the infliction of suffering on them.

The new freedom of expression brought by the Internet goes far beyond politics. People relate to each other in new ways, posing questions about how we should respond to people when all that we know about them is what we have learned through a medium that permits all kinds of anonymity and deception.

Were we incapable of empathy – of putting ourselves in the position of others and seeing that their suffering is like our own – then ethical reasoning would lead nowhere. If emotion without reason is blind, then reason without emotion is impotent.

Sci-fi is often a metaphor. I think it's more the themes and questions that science fiction raises rather than the exact predictions that should guide us.

Ancient recipients of instant news probably couldn't do very much about it, for instance. Xerxes would still need three months to get his army together, and he might not get home for years.

We need to learn how to capture and kill wild fish humanely - or, if that is not possible, to find less cruel and more sustainable alternatives to eating them.

There is an obvious evolutionary explanation for the scarcity of altruistic saints: Without a strong predilection for their own interests, our ancestors would have been unlikely to survive, reproduce, and give their own offspring a chance of doing the same. Now conditions have changed and for most of us, surviving and reproducing isn't such a struggle but we still carry the genes of our ancestors and they influence - not determine, but influence - our behavior.