Religion is something left over from the infancy of our intelligence, it will fade away as we adopt reason and science as our guidelines.

I say quite deliberately that the Christian religion, as organized in its Churches, has been and still is the principal enemy of moral progress in the world.

It is possible that mankind is on the threshold of a golden age but, if so, it will be necessary first to slay the dragon that guards the door, and this dragon is religion.

One should respect public opinion insofar as is necessary to avoid starvation and keep out of prison, but anything that goes beyond this is voluntary submission to an unnecessary tyranny.

There is no need to worry about mere size. We do not necessarily respect a fat man more than a thin man. Sir Isaac Newton was very much smaller than a hippopotamus, but we do not on that account value him less.