There is a tendency among those who grew up under the rule of law to treat it like the Rock of Ages, an immovable substrate in which all the institutions of the state are forever anchored. And so even ordinarily skeptical people tend to assume that the government obeys its own laws when no one is looking. To an astonishing extent, and to the great credit of American civic life, this is actually true.

But I think a better metaphor for the rule of law is that it is the soil in which democratic institutions take root. Like the soil, it can be depleted. And once depleted, it is not easily replenished. Secrecy erodes the rule of law because it makes democratic accountability impossible. Secrets can’t be held too broadly, so secrecy concentrates responsibility and asks too much of human nature. That is why every intelligence agency, unless given rigorous outside oversight, commits terrible excesses.

—Maciej Ceglowki’s response to David Simon’s shrug about the NSA’s domestic spying system is vitally important.