Becoming a vegan is a sure way of completely avoiding participation in the abuse of farmed animals. Vegans are a living demonstration of the fact that we do not need to exploit animals for food.

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.

The problem is not with the athletes, but with us. No matter how blatant the drug use may be, we don't stop watching the Tour de France. Maybe we should just turn off the television and get on our own bikes.

The newspapers do little better. Their coverage of nonhuman animals is dominated by "human interest" events like the birth of a baby gorilla at the zoo, or by threats to endangered species; but developments in farming techniques that deprive millions of animals of freedom of movement go unreported.

In appropriate circumstances we are justified in using humans to achieve goals (or the goal of assisting animals).

I am not saying that factory farming is the same as the Holocaust or the slave trade, but it's clear that there is an immense amount of suffering in it, and just as we think that the Nazis were wrong to ignore the suffering of their victims, so we are wrong to ignore the sufferings of our victims.

Of all the arguments against voluntary euthanasia, the most influential is the slippery slope: once we allow doctors to kill patients, we will not be able to limit the killing to those who want to die.