Political alliances are, to use what is probably an inappropriately martial metaphor for this column, a double-edged sword. Effectiveness on a particular policy choice usually requires working closely not only with people who align with you on that issue but not many others, but also collaboration with those whose reasons for that specific agreement differ sharply from yours.

Two examples illustrate the first point.

As a defender of the working people engaged in the fishing industry in the New Bedford, Massachusetts, area, I joined deeply conservative members from other districts where fishing is important in seeking to reform unjustified, arbitrary rules and unfair administrative procedures.

And I am proud that the first two members of Congress actively to advocate repeal of the federal law criminalizing marijuana were Ron Paul and myself. In both cases, while we differed on almost every other issue, our reasons for seeking these specific policy changes were essentially similar.

In the second situation, where people find themselves on the same side but for very different reasons, that point is often not sufficiently emphasized. No one confused Ron Paul’s consistent opposition to government action in general with my position that there is a need for effective regulation of economic affairs but not for dictating purely personal choices.

But on other issues, in their understandable enthusiasm for a shared goal, advocates – not necessarily consciously – tend to gloss over fundamental disagreements on why it is desirable.

The most striking current example of this phenomenon is the debate over the question of the global role of America’s military, especially but not entirely in Afghanistan and the Middle East.

I am pleased that some of the most ardently conservative activists, including many in the tea party wing, oppose an essentially unlimited military budget, the return of American troops into Iraq and Afghanistan and the introduction of our forces on the ground in Syria. In what I hope will not be seen as excessive self-praise, I am also proud that the last successful amendment I co-sponsored was with Rep. Mick Mulvaney of South Carolina, a leading House conservative, to reduce the defense appropriation.

But it is very important for those of us on the left who argue for much more restraint in the use of American military force – and consequently in our budgeting for the Pentagon – to differentiate our reasons for doing so from many of those on the right.

Specifically, we must be explicit that we repudiate the view that America’s focus should be almost exclusively our own self-interest and that poverty, disease, disaster and oppression elsewhere in the world are not our concern.

I reject the idea that it is our responsibility to preserve global order – to be the world leader with an obligation to intervene whenever disruption threatens stability anywhere, anytime, anyplace.

I know there are those who think I exaggerate in imputing this view to the McCain-Graham-Ayotte faction of the Republican Party, which now includes most Republican candidates for president. (No one can plausibly claim to be able to keep track of all of them.)

I refer them to the op-ed column in the Wall Street Journal – itself a firm advocate of this position – the day after the 2012 election, in which a former Bush administration Air Force official laments that a re-elected President Obama will fail to increase the Air Force so that it has the capacity to do exactly what I just wrote.

But it is intellectually and politically important to make clear that rejection of a global policing role for the U.S. is not only wholly compatible with support for an active American role in trying to improve the quality of life elsewhere, especially in the poorer parts of the world. The practical and moral arguments for both military restraint and economic and social activism have the same basis: a recognition that our wealth and influence can be a positive force as long as we also recognize the limits on the ability of even the most powerful nation to engineer fundamental changes in any other society, and that any effort to do so is highly likely to do more harm than good.

Again, a specific piece of history illustrates the point – the difference between liberal opponents of further deeper military engagement in Iraq, Afghanistan and Syria and those conservatives with whom we are allied on this issue.

That is the case of Ebola. There is no greater example of completely unjustified, inaccurate, demagogic criticism of Obama than the bitter denunciation of his refusal to seal off America from those African countries in which the disease was raging.

Barney Frank is a retired congressman and the author of landmark legislation. He divides his time between Maine and Massachusetts.

Twitter: BarneyFrank