Testifying on Capitol Hill on Thursday, FBI Director Christopher Wray walked a tightrope on the so-called "Steele dossier."

Compiled by Christopher Steele, a highly respected former member of Britain's Secret Intelligence Service (the SIS is Britain's equivalent of the CIA), the dossier contains a range of highly personal reports pertaining to possible activities by President Trump in Russia and Russian intelligence operations targeting the United States.

But when asked why the FBI hasn't handed over more information on the dossier, Wray stated that it affects ongoing investigations including that led by special counsel Robert Mueller. This was an interesting comment in that Wray is suggesting the FBI believes the dossier has some measure of veracity or has otherwise opened up new lines of investigation.

But then Wray raised a different perspective on why he doesn't want to provide more information to Congress.

When it comes to the dossier, Wray said, "We are dealing with very, very dicey questions of sources and methods. Which is the lifeblood of foreign intelligence and for our liaison relationships with foreign partners."

The "very, very dicey" comment speaks to concerns that have been raised in regards to the identity of some of Steele's sources, and the honesty and purpose of their information. Coming from the FBI director, the "dicey" description will give Trump and his inner circle some measure of confidence that Wray is skeptical of the dossier's import.

Still, it's also very interesting that Wray mentioned the "lifeblood" of foreign intelligence liaison relationships as a reason for not providing more information to Congress. Here the director would seem to be referring to intelligence sources in the Steele dossier that are controlled by foreign counterparts. Considering Steele is a former head of the SIS' Russia desk, it would figure that some of the sources in his dossier might still be working with the British government on other issues.

That would be the most obvious explanation for why the FBI doesn't want to share too much information with Congress: they know that if anything leaks, it might compromise British intelligence sources in Russia. That would be a catastrophic breach in the U.S.-U.K. trust-based intelligence cooperation relationship, which remains the closest of any two intelligence services around the world. For that reason alone, Wray will go to the wall to protect British secrets.

Ultimately, all of the above might be wrong. And in that regard, Wray's comments speak to "the wilderness of mirrors" that defines many human intelligence operations: it's hard to know what's real and what's not, and what's important and what not, and whether those concerns might constantly be shifting.