SOCRATES: Because our eyes are delicate, they have been shuttered with eyelids that open when we have occasion to use them . . . And our foreheads have been fringed with eyebrows to prevent damage from the sweat of the head . . . And the mouth set close to the eyes and nostrils as a portal of ingress for all our supplies, whereas, since matter pass

Conjectures are the products of creative imagination. But the problem with imagination is that it can create fiction much more easily than truth.

Just as the spaceship’s life-support system is designed to sustain its passengers, so the biosphere has the ‘appearance of design’: it seems highly adapted to sustaining us (claims the metaphor) because we were adapted to it by evolution. But its capacity is finite: if we overload it, either by our sheer numbers or by adopting lifestyles too differ

It is inevitable that we face problems, but no particular problem is inevitable. We survive, and thrive, by solving each problem as it comes up. And, since the human ability to transform nature is limited only by the laws of physics, none of the endless stream of problems will ever constitute an impassable barrier. So a complementary and equally im

What was needed for the sustained, rapid growth of knowledge was a tradition of criticism. Before the Enlightenment, that was a very rare sort of tradition: usually the whole point of a tradition was to keep things the same.

Experience is indeed essential to science, but its role is different from that supposed by empiricism. It is not the source from which theories are derived. Its main use is to choose between theories that have already been guessed. That is what ‘learning from experience’ is.

Lamarckism. Its key idea is that improvements acquired by an organism during its lifetime can be inherited by its offspring.

Another assumed characteristic of the designer according to most religions is benevolence. But, as I mentioned in Chapter 3, the biosphere is much less pleasant for its inhabitants than anything that a benevolent, or even halfway decent, human designer would design. In theological contexts this is known as ‘the problem of suffering’ or ‘the problem

gold can be created only by stars and by intelligent beings. If you find a nugget of gold anywhere in the universe, you can be sure that in its history there was either a supernova or an intelligent being with an explanation. And if you find an explanation anywhere in the universe, you know that there must have been an intelligent being. A supernov