When you do the right thing, but not to any particular person, we instinctively feel that we have earned some sort of pay back. Since no-one will do that for us, we opt for self-service reciprocation.

Since Plato, we have been considering the nature of knowledge, the meaning of meaning and the status of the physical world.

If there's one thing that makes me cynical, it's optimists. They are just far too cynical about cynicism. If only they could see that cynics can be happy, constructive, even fun to hang out with, they might learn a thing or two.

A lot of religious belief - even the majority - involves making factual claims about the world which do come into conflict with science and history. For Christians, a test of this is the Empty Tomb. I ask Christians: 'are you saying that it does not matter - as a matter of fact - whether or not Christ's tomb was empty and that he was resurrected?' At that point, I find that, to a lot of them, it really does matter, despite all the fine talk about not wanting to confuse science and history with religion.

The border between the natural and the supernatural, religion and philosophy, may not always be clear. But there are lines and we should know and accept which side of it we are on.

I am very Aristotelian in approach - not in detail - so I always find I'm saying things that get people frustrated like 'It's a matter of balance and judgement'. To a lot of philosophers these are terrible words because they're admitting of vagueness and uncertainty. The more I've done philosophy, the more I've become convinced that that is the way it is.

The reason Buddhism can be so naturalised is because, stripped of its supernatural elements, its core teachings can be giving a sound, secular philosophical interpretation. In other words, it becomes a religion acceptable to the contemporary, naturalistic mind only when it ceases to be a religion.