At this moment, we are in no better position than we were yesterday to provide informed hypotheses about who may have carried out the bombing attack and why. We don’t know what the investigators know, but on our state of information, it would be irresponsible to discount the possibility that this is an instance of jihadist terror. Of course, other ideological motivations cannot be ruled out, either. My point is that it is ludicrous to enforce a politically correct filter in which the most plausible explanation must not be spoken on pain of being cast out as a racist “Islamophobe,” yet every other theory, no matter how half-baked, is given a respectful airing.

We know that jihadists tend to target predominantly non-Muslim civilian populations with mass destruction weapons, as was done in Boston on Monday. In addition, their preferred weapon for the last decade in Iraq and Afghanistan has been the improvised explosive device (IED) — the kind of home-made bomb that is recommended by al Qaeda’s Inspired Magazine and that often employs “pressure cookers” of the sort used in two recent jihadist terror attacks in the U.S. The attacks on Monday were by IEDs that featured pressure cookers. None of that proves that the Boston Marathon bombing is the work of jihadists, but it does underscore that — absent hard information pointing in a different direction — it is entirely reasonable to suspect that this is the case and to investigate accordingly.

By contrast, we haven’t had much “anti-government” terrorism but when we’ve had it — e.g., the 1995 Oklahoma City bombing — it tends to be targeted at government installations, not civilians. And historically, the radical Left is far more wedded to violent “direct action” than conservative movements like the Tea Party, which has no history of violence. It should go without saying that we have had terrorists of varying political stripes, and even of no coherent political persuasion. Therefore, no radical ideology that urges violence should be ruled out at this point when, apparently, no perpetrators have been identified. How strange, though, that what experience suggests are the least likely scenarios — conservatives or anti-government extremists striking savagely at their defenseless fellow citizens — are being embraced seriously (even wistfully) by some media pundits, while one must walk on eggshells to describe scenarios whose proving out would surprise no one.

Finally, and eerily reminiscent of the post-9/11 anthrax scare, is the discovery that letters addressed to the president and Senator Wicker (so far) contained a granular substance that has, according to the FBI, “preliminarily tested positive for ricin.” NBC News has just reported that federal agents have arrested a Mississippi man, Kenneth Curtis, in connection with the mailings (which were signed, “I am KC and I approve of this message.”).

At least at this early stage, investigators are said to believe that there is no connection between the mailings and Monday’s bombing in Boston. That certainly sounds like a reasonable conclusion under the circumstances: Putting aside that Curtis is from Mississippi, the letters were postmarked in Memphis, Tennessee, on April 8 — a week before the bombing in Boston; and more testing and investigation are necessary before the feds can confidently conclude that the substance involved is actually ricin and that it was intentionally conveyed by the sender. Until there is certainty that the two incidents are unrelated, though, the lines of communication between the two investigations must remain open.