We have to gamble, and sometimes lose as George Ainslie argues; this keeps the appetite for life sharp.

We are now returning to the 18th century empirical approach with the new interest in the evolutionary basis of ethics, with 'experimental' moral philosophy and moral psychology. As a result, we understand better why moral formulas are experienced as ineluctable commands, even if there is no commander and even if the notion of an inescapable obligation is just superstition. So moral philosophy has made huge progress.

The Epicureans denied that the gods had created the world and also denied that they played any role in it.

Some critics thought the ontology and theory of qualities absurd. No one had ever seen these little atoms, and furthermore, how could their mere arrangement produce a noisy, colourful, world in which day followed night and animals generated their own kind? Instead of a world created, cared, for and supervised by supernatural persons, the Epicureans appeared to the theologians to be assigning everything to chance. The latter were appalled by Lucretius's view of religion as cruel and oppressive and by the Epicurean insistence that death is the end of all experience.

You can reasonably make the intellectual journey from thinking it's permissible to eat shrimp to thinking it's not permissible, or vice versa, whereas our slavery journey was uni-directional. We are as certain we are not going back to that old kind of slavery as we are that we aren't going back to the geocentric universe.

Even if you just want to make a simple clothing item for yourself or go for a long hike in the forest - something we imagine requires absolutely no resources - you have to go to the store and buy a lot of stuff, and probably use a car.

Morality has in the past made progress when we broadened the category of things we weren't permitted to harm (animals, 'infidels'); saw through some delusions and rationalisations about what harms are good for people themselves (prison punishment, hysterectomies for unhappy 1950s wives); and readjusted our for-the-good of others criteria so as to demand only reasonable sacrifices (ceasing to use children as handy chimney sweeps).