Few scientists now dispute that today's soaring levels of carbon dioxide and other gases in the atmosphere will cause global temperature averages to rise by as much as nine degrees Fahrenheit sometime after the year 2000.

If we say that God has always been, why not save a step and conclude that the universe has always been?

Science ... looks skeptically at all claims to knowledge, old and new. It teaches not blind obedience to those in authority but to vigorous debate, and in many respects that's the secret of its success.

[Science] is not perfect. It can be misused. It is only a tool. But it is by far the best tool we have, self-correcting, ongoing, applicable to everything. It has two rules. First: there are no sacred truths; all assumptions must be critically examined; arguments from authority are worthless. Second: whatever is inconsistent with the facts must be discarded or revised. ... The obvious is sometimes false; the unexpected is sometimes true.

We can judge our progress by the courage of our questions and the depth of our answers, our willingness to embrace what is true rather than what feels good.

Advances in medicine and agriculture have saved vastly more lives than have been lost in all the wars in history.

The hole in the ozone layer is a kind of skywriting. At first it seemed to spell out our continuing complacency before a witch's brew of deadly perils. But perhaps it really tells of a newfound talent to work together to protect the global environment.