Political figures get away with blatant inconsistency far too easily. The most frequent defense is the misstated quote from Ralph Waldo Emerson, who in fact wrote: “A foolish consistency is the hobgoblin of little minds.”

It is foolish to stick to a point in the face of new evidence or to refuse ever to change your mind. But when the advocate of a given ideological viewpoint regularly shifts among logically or factually inconsistent arguments to defend particular policy choices, it is a sign of two things: first, intellectual dishonesty; second, an implicit acknowledgment that the advocate’s substantive position is either too unpopular or too weakly reasoned to win support on its own – or both.

The latter point is the central one for judging political debates. Rather than defend a controversial position on its merits, its supporters will often invoke a more widely accepted general principle and claim that all they are doing is invoking it in a specific case. But when those same people cite the exact opposite of that overarching point to justify a different course of action, it is clear that they are not defending a broader principle, but hiding behind it to win an argument they would lose on its individual merits.

My most recent encounter with this “debate and switch” maneuver came last Monday, when I discussed the Patriot Act with William Kristol on MSNBC’s “Morning Joe.” Kristol is a leading conservative defender of the war in Iraq and other vigorous American military intervention in the Middle East and an opponent of the fortunately successful recent effort to put some restraints on the government’s information-gathering power under the Patriot Act.

Kristol is one of those repentant ex-liberals who is wholly skeptical of our ability through government to do much to diminish inequality at home. For example, he is proud of his role in insisting that conservatives do everything possible to kill expanded health care when Hillary Clinton pushed for it in 1993 and helped ensure unanimous Republican opposition to President Obama’s Affordable Care Act.

Knowing of his passionate arguments that government must not be trusted with the expanded authority to help Americans receive adequate health care, I was bemused by his equally vigorous insistence that there is no reason at all to be skeptical of either the competence or the undiluted good intentions of that same government where national security is concerned. To those who fear that masses of personal information in government hands could lead to misuse, his response is that we can be sure that it will be safeguarded by those who have it. When challenged by the fact that the defenders of the extensive information-gathering power have not been able to cite – even under tight security – any case where it helped stave off an attack, his response was that he trusts these public officials and when they say they need all of the authority they have had since 9/11, his respect for them dictates agreement, with no requirement that they justify their stance.

This illustrates the point. Kristol is opposed to an increased government role in extending health care or diminishing inequality. He expressed his disapproval of a Wal-Mart ad about its decision to raise its minimum wage. He disapproved on philosophical grounds, but knowing that these goals are popular with the public, like his fellow conservatives, he bolsters his case by denigrating the government, run as it is by bureaucrats seeking to enhance their own power and lacking the competence to execute complicated programs. But when the question is giving this same government extensive powers over much of our private communication with virtually no judicial oversight, and severely constrained congressional supervision, Kristol and his conservative allies sleep soundly, comforted by their complete faith in that government.

The lesson is clear. Conservatives are not skeptical of an assertive, even intrusive, government as long as they agree with the purpose for which it is exercising great power. They oppose even less extensive federal authority in the domestic economic realm because of their ideological disagreement with its social goals, not because of some nonexistent principled objection to government authority in general.

Nor is this the only example of this very selective invocation of broad principles by conservatives as they defend their narrower, more specific goals. Their position on when a chief executive should act on his own and when he must receive legislative approval is an even more important one, relating to the issue of when America should go to war. I will discuss this next week.

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

Twitter: BarneyFrank