At every level the greatest obstacle to transforming the world is that we lack the clarity and imagination to conceive that it could be different

I regard myself as a man without charm in a country of charmers.

In a world of democracies, the most deserving basis of national differences is that the different states of the world should represent a form of moral specialisation within humanity.

The Amazon is not just a set of trees. It is a set of 25 million people. If we don't create real economic opportunities for them, the practical result is to encourage disorganized economic activities that results in the further destruction of the rain forest.

In a world of democracies, in a world where the great projects that have set humanity on fire are the projects of the emancipation of individuals from entrenched social division and hierarchy; in such a world individuals must never be puppets or prisoners of the societies or cultures into which they have been born.

When we imagine our Universe to be just one out of a multitude of possible worlds we devalue this world, the one we see, the one we should be trying to explain.

The scientist should treasure the riddles he can't solve, not explain them away at the outset.