John Derbyshire thinks there's a tension between liberalism and science:

liberal scientists, which is to say most scientists?are stuck in an uncomfortable philosophical fork.

Liberalism is optimistic. It is a doctrine of progress and improvement. (Why do you think they call themselves ?progressives??) In this, liberalism has had the support of science, which has made so much improvement possible ? banishing diseases, improving the quality and variety of our food, reducing the need for arduous labor, increasing our comfort and amusements.

The link between liberalism and science is therefore easy to understand. Along with the generally optimistic implications of scientific progress, though, there has always been a pessimistic undertow. By repeatedly dethroning us ? not at the center of the universe, only another branch on the tree of life ? science diminishes us in our own eyes.

But as part of a dynamic universe governed by laws, you can improve yourself. You don't need to be perfect, or the center of things. Indeed, the same reasoning that tells us we aren't the center of things means that no one else is either. And that's not cause for pessimism (nor, inherently, for optimism). Things could get worse, and a pessimist is entitled to remain a pessimist. But an optimism has plenty to work with, too.

Joel Mathis objects to a different part of that passage:

I can't speak for others who call themselves liberal, but I think my liberalism has generally stemmed from a deep well of pessimism. Just to pluck out three examples...

? I think that over time, an un- or under-regulated market will accrue all or most of the rewards to the people who already have the most resources, generally squeezing workers who actually do much of the wealth creation in that market.

? I think that, without a government to step in and safeguard everybody's rights, majorities will generally stomp on the neck of minorities?be they racial, religious, or sexual minorities.

? I think that when we go to war abroad, lots of people whom we never think about get killed. That it generally costs more and lasts longer than we're promised.

So I favor regulated markets, the rule of law, and a dovish foreign policy. Not because?as conservatives allege?I expect government to create some kind of heaven on earth. I know that's not possible. But I think government can curb our worst tendencies and mitigate their results.

Conservatives who are willing to grant any of those premises, though, essentially throw up their hands. They'll grant that markets aren't always good for everyone, but they'll insist that government intervention would just make it worse. Or sure, Jim Crow laws are an affront to American standards of decency, but government can't just impose integration on the South, we just have to leave it for folks to sort that out on their own. And so forth.

In other words, both sides acknowledge the facts on the ground, an acknowledgment which Joel considers pessimistic. But what makes him (and me!) liberals is that we think something can be done about that. We think that government regulations can make markets fairer. We think government actions can improve the lot of oppressed minorities. We think government action can avert or at least alleviate the suffering caused by war.

And in practice, that optimism (in the capacity of government to do things) has been repeatedly vindicated. The Marshall Plan, the New Deal, civil rights laws and the Great Society all show government doing exactly these things, in ways that strengthen society and even out damaging inefficiencies. We've seen the same benefits from the stimulus bill, and from Affordable Care. There are comparable gains to be seen from enacting climate change policies.

Conservatism is pessimistic in that it rejects the possibility of fixing problems. And if you don't think you can fix a problem, you often try to ignore that it exists (as we see with global warming denial). Liberalism is not pessimistic for acknowledging that problems exist, it would only be pessimistic if it gave up on the idea of fixing those problems.

And, for what it's worth, when I talk about optimism about government doing things, what I really mean is optimism about the ability of people to get together and solve collective problems through a shared process. Governments exist not as some abstract imposition on society, but as a way to formalize this sort of social problem solving, an activity that primates have done since before humans existed.

Finally, another note on Derbyshire: he qualifies his argument that science is optimistic by writing: "Science ? more precisely the technology that science makes possible ? has fueled much of that political optimism."

This equation, often unacknowledged, of science and technology, is common and problematic. Problematic in part because it leads to exactly the sort of optimism Derbyshire is espousing. Conservatives like Newt Gingrich are often enthusiastic about funding the sorts of research that will lead to technological advances (including space exploration, biomedical research, etc.), but are less enthusiastic about basic research, or research oriented towards identifying a problem or exploring its full scope. Hence, Bush-era suppression of climate science, or Rick Scott's recent attack on the state of Florida's Everglades management unit. Conservatives would happily fund expensive schemes for carbon sequestration, or other complex technological systems that could let us keep burning coal without having to worry about global warming, but scientific research that shows global warming happening is anathema.

There's obviously substantial overlap between science and technology, but they aren't identical, and while stories of technological progress can inspire a sort of optimism, we should balance that optimism with reminders of technological failure (including the persistence unintended consequences, like the accumulation of greenhouse pollution as a result of the internal combustion engine).

On the other hand, the expansion of knowledge thanks to science is always cause for optimism. Even scary findings, like the relatively sudden discovery of the ozone hole in the 1980s, are good, because knowledge is a good thing. With knowledge comes opportunity and responsibility. That's neither cause for optimism nor pessimism.

I believe in humanity, and that means I believe in the ability of government of the people, for the people, to fix people's problems. That's why I'm an optimist, and a liberal.