So, there’s an ongoing Fight on the Internet (TM) between what you might call the Civil Liberties Left (whose most outspoken member is probably the Intercept’s Glenn Greenwald) and the Progressive Left (whose most notable tweeter, in this debate, is probably Vox’s Matt Yglesias) over what Attorney General William Barr’s summary of special counsel Robert Mueller’s report about the 2016 election means.

Greenwald and others in his camp believe that the summary’s conclusion that no one on the Trump campaign “conspired or coordinated with the Russian government in its election interference activities” is evidence the liberal media’s coverage of Trump and Russia for the last two-plus years has been hysterical, xenophobic conspiracy-mongering. Yglesias, meanwhile, has noted that the Barr letter concludes that Russia engaged in extensive “election interference,” which is a claim that Greenwald has been skeptical of, while New York’s Eric Levitz and the New York Times’ Jamelle Bouie have pointed out that Trump could still have engaged in Russia-related behavior that was ethically corrupt and dishonest even if Mueller decided it wasn’t illegal per se.

The central question that could resolve this debate, to the extent that internet arguments can ever be resolved, is why Mueller (apparently) chose not to make a case that Trump and his top advisers participated in an election-interference conspiracy by discussing U.S. sanctions against Russia with representatives of the Russian government. Which is a question that’s important not just because it might end a Twitter feud, but because it would, you know, help the American public understand what the hell their current president was up to during the year that his advisers kept discussing U.S. policy with the foreign power that was sabotaging his campaign opponent.

To review:

• Russia does not like that the U.S. has imposed sanctions that restrict a number of Russian political figures and oligarchs from using the U.S. financial system.

• It’s a noncontroversial matter of public record that Russians with connections to the Russian government met with Donald Trump Jr., Paul Manafort, and Jared Kushner at Trump Tower in New York City on June 9, 2016, in part to complain about sanctions.

• In response to claims by the special counsel’s office, Paul Manafort’s attorneys have admitted that he met on Aug. 2, 2016 in New York City with an individual named Konstantin Kilimnik to discuss topics including a Ukraine peace plan. It’s a matter of public record that Kilimnik received language training from the GRU, Russia’s military intelligence agency, and the special counsel has asserted that Kilimnik still had active ties to Russian intelligence in 2016. It’s also a matter of public record that Russia wants to resolve the Ukraine situation in part because doing so might result in the lifting of sanctions.

• Former national security adviser Michael Flynn has admitted in court filings that he discussed sanctions in a telephone conversation with Russia’s ambassador to the U.S. during the presidential transition period.

Mueller was clearly interested in the June 9 meeting, the Manafort-Kilimnik meeting, and the Flynn conversation. The question, then, is whether he decided that Trump and his advisers’ conduct in relation to those incidents was entirely defensible and above-board (which would tend to support Greenwald’s position) or whether he found the incidents concerning and corrupt but not necessarily prosecutable (which would support Yglesias et. al’s positions).

As my colleague William Saletan points out, it’s possible that Barr selectively quoted Mueller to make it appear that his report clears Trump of any inappropriate interaction with Russia when in fact Mueller’s full report simply addresses the sanctions issue as separate from “election interference” because it didn’t directly involve hacking or distributing Democratic emails. There’s also a related possibility, hinted at in this Daily Beast report, which is that Mueller felt the question of whether the sanctions talk was criminal was best left to Congress, because it involves a sitting president:

A source with direct knowledge of the investigation told The Daily Beast that it was their interpretation that “Mueller was making a case to Congress, who (unlike DOJ, in Mueller’s view) is empowered to weigh the lawfulness of a president’s conduct.”

The Daily Beast’s quote is tantalizingly light on context; it’s not clear whether the source was referring to a “case” for conspiracy charges, or obstruction charges, or both, or something else—or how exactly Mueller would have been under the impression that he’s making a case to Congress when his report was submitted to the attorney general, who has discretion over what parts of it to release.

There would be an easy way to resolve all of this, which is to ask Robert Mueller, and there doesn’t appear to be anything that would preclude him from appearing before Congress to answer questions about how he defined “coordination.” But while Democrats on the House Intelligence Committee say they’re interested in calling Mueller in to discuss “broader” counterintelligence issues, the Dems leading the House Judiciary Committee—which would be directly responsible for the impeachment-related question of whether the president committed a crime—have not expressed a similar intention. I put in an inquiry with the committee about the possibility but haven’t heard back. They should definitely do it, for America/Twitter.