For many years, my former colleague Justin Logan had an editorial cartoon posted on his door in which two scholarly looking men are reviewing a long and convoluted proof scrawled on a blackboard. Amidst the incomprehensible symbols and numbers, somewhere between the beginning and QED, is written, “Then a miracle occurs.”

One turns to the other and says, “I think you should be more specific here in step two.”

This message seems sadly relevant given that presidential candidates on both sides of the aisle have been quick to describe what they plan to do to defeat ISIS. It isn’t enough, however, for these men and women to tell us what actions they would take. It is also incumbent upon them to explain, as precisely as possible, what they believe will happen as a result.

For example, although Hillary Clinton has supported and supervised military interventions in more countries than all of the GOP candidates put together (ponder that for a minute), she apparently feels the need to burnish her hawkish credentials. Last week, in a speech before the Council on Foreign Relations, she called for an “immediate war against an urgent enemy and a generational struggle against an ideology with deep roots.”

Clinton certainly isn’t the most hawkish candidate out there. NPR assembled a helpful table, complete with links, to the candidates’ views on a range of ISIS-related policies, from blocking Syrian refugees, to sending in U.S. ground troops, to imposing a no-fly zone.

Anyone who promises to take some form of military action or diplomatic pressure to defeat ISIS should be asked the same question: “And then what happens?” Or, more formally, “Please explain, to the best of your ability, how the particular action that you are advocating will accomplish your stated ends. Show your work. Use both sides of the paper if necessary.”

Because international politics isn’t subject to iron laws of arithmetic or gravity, a fair amount of speculation and supposition goes into the making of foreign policy. We guess as to what might happen after a particular course of action is chosen, supported by reasonable assumptions, given the facts on the ground at that particular time and informed by past experience in similar situations. But both the facts and the assumptions should be scrutinized.

Reasoning by analogy is a perilous enterprise, as Ernest May showed many years ago, and can lead to misinterpretation or misjudgment as often as it leads to sound solutions to vexing problems. (This applies in the case of businesses, too.)

In Myths of Empire, Jack Snyder addressed a particular type of misconception, what he calls the paper tiger thesis. On the one hand, a foreign threat is deemed serious enough that preventive action is warranted to eliminate it. On the other hand, the capabilities of the adversary in question are not so serious that he won’t be easily vanquished after a short and swift drubbing. Past instances in which this was true are cited to support the case for war—while the cases that do not conform, when an attacked adversary didn’t tuck tail and run after being hit, are dismissed as inapplicable. The risks of inaction are always portrayed as very high (case in point: here) and the risks of action are deemed to be negligible.

Snyder shows that the paper tiger thesis isn’t a very good foundation for the conduct of foreign policy, generally, but it seems particularly appropriate today, in light of the news that a Turkish F-16 shot down a Russian SU-24 and killed at least one Russian, to suspend any inclination to go along with the interventionists’ story, and not simply accept their assumptions about cause and effect. We should especially challenge the facile claims that all will go according to plan—that the bad guys will crawl back into their holes, or simply curl up and die—when the risks of preventive action are very high. Not every brushfire war will turn into a major conflagration between nuclear-armed states (thankfully), but the chance that it might should give all of us pause.

Christopher A. Preble is vice president for defense and foreign policy studies at the Cato Institute.

Image: Flickr/Joe Crimmings