The thing that defines a species is that all members have the same addressing system for their DNA.

The cynic about human nature might say that religious morality is an effective way of keeping people in line. The threat of hell, the reward of heaven, but the rules of the holy books are out of date and often barbaric.

I am thrilled to be alive at time when humanity is pushing against the limits of understanding. Even better, we may eventually discover that there are no limits.

Ironically, I originally wrote the tweet with Jews and thought, That might give offense. And so I thought I better change it.

Individuals are not stable things, they are fleeting. Chromosomes too are shuffled into oblivion, like hands of cards soon after they are dealt. But the cards themselves survive the shuffling. The cards are the genes. The genes are not destroyed by crossing-over, they merely change partners and march on. Of course they march on. That is their business. They are the replicators and we are their survival machines. When we have served our purpose we are cast aside. But genes are denizens of geological time: genes are forever.

I personally would go further and say that, if your morality is based, as mine is, on a desire to increase the sum of happiness and reduce suffering, the decision to deliberately give birth to a Down baby, when you have the choice to abort it early in the pregnancy, might actually be immoral from the point of view of the child’s own welfare.

People will listen to sophisticated physicists, using God as a kind of metaphor for the deep constants, the deep problems, the deep principles of physics, and say that in that sense I believe in God. The reaction is, "Oh, this great physicist believes in God - that means I'm free to believe in the trinity and in the crucifixion and in the reincarnation of Christ" - and all that stuff, which of course has nothing whatever to do with the fundamental constants of physics, which is what these physicists are talking about.