Matthew Yglesias takes a stab at defining one:
'So my best cut at articulating the difference in a high-level way is that the right sees the world as zero-sum. Arrangements that advance the interests of others are inherently suspect because the mere fact that (say) the Russians think a deal is worth signing indicates that it must be bad for the United States. Progressives see a positive-sum world and believe in advancing American interests by means that including allowing others to advance their own interests. Progressives recognize the Hobbesian aspects of the international system that make positive-sum interactions difficult to obtain, but we see this as a challenge that can be overcome and seek means of overcoming it. Conservatives, meanwhile, are perpetually tempting fateâ??by sending the message to the world that America cares most about preserving its power relative to others, we indicate that the only way for others to advance their interests is by undermining our position.
'
First, I think Ygelsias is somewhat misrepresenting that dominant conservative position. I'd argue that conservatives seem to agree that some aspects of the world are indeed positive sum: the U.S. military as a global police force protects our interests but also lets allied states peacefully pursues theirs. They do not see the accumulation of U.S. power as a zero-sum affair because American power supports the positions and interests of a host of other nations.
While I'm skeptical of the idea of perpetual global hegemony, I'm not sure how much faith we can place in the progressive ideal sketched by Yglesias above. After all, what if other nations do view international affairs as a zero-sum conflict? We don't have the luxury of opting out of international competition just because we view the idea as anachronistic. It's one thing to take a magnanimous view of mutual interest when your country has the preponderance of power, but what if that changes?
Moreover there seems to be a glaring contradiction between a progressive foreign policy built around strengthening mutual interests and a progressive domestic policy that is deeply critical of international trade.