Thursday marks a year since Robert Mueller was appointed as special counsel to oversee the Russia investigation, and in that time I’ve written a lot about the known unknowns of his work. We don’t know everyone he’s interviewed. We don’t know what evidence he’s gathered. We don’t know what further charges he may bring against people around the president. We don’t know if he’ll recommend that Congress open impeachment hearings for President Donald Trump.

But we also know quite a bit about Mueller’s work since last May. All the available evidence indicates that he’s running a competent, disciplined, and thorough investigation. He’s maintained those standards under extraordinary circumstances on a matter of immense national consequence. And he’s upheld the inquiry’s integrity even while Trump threatens to fire him and Republicans in Congress continually try to undermine his work.

Americans are drawn to bold figures who rise above politics and clean up Washington. Trump played to that cultural bias during the campaign, portraying himself as an outsider whose wealth would insulate him from corruption and empower him to “drain the swamp.” But it’s Mueller, if anyone, who fits this cultural archetype. Over the past twelve months, the former FBI director has upheld the best traditions of the American civil service, rightly becoming an icon for the rule of law in an era when the concept itself is under siege.

One of the most startling things about Mueller’s inquiry is how rapidly it has advanced. Patrick Fitzgerald, the last high-profile special prosecutor to vex a presidency, went silent for almost two years after his appointment in 2003 to investigate who leaked the identity of covert CIA operative Valerie Plame. (He dramatically resurfaced to announce charges against Scooter Libby, whom Trump pardoned last month in what many saw as a veiled threat to Mueller. Fitzgerald recently joined former FBI Director James Comey’s legal team.)

By comparison, Mueller’s investigation has been action packed. He’s brought charges against 19 people to date in the past six months. Thirteen of them are Russians, effectively beyond Mueller’s reach. The other six defendants aren’t so lucky. He’s secured plea agreements from former national security advisor Michael Flynn, former Trump campaign deputy chairman Rick Gates, and former Trump foreign-policy aide George Papadopoulos, all of whom have agreed to cooperate in exchange for lighter sentencing. Richard Pinedo pleaded guilty to supplying Russians with bank account numbers, while Dutch lawyer Alex van der Zwaan received a 30-day sentence for lying to investigators. The trial of Paul Manafort, Trump’s former campaign chairman, is expected to begin this summer.