In a telephone conversation with President Obama a few months ago, German Chancellor Angela Merkel is reported to have suggested her Russian counterpart is "living in another world."
Just last week, a leaked report commissioned by the U.S. Defense Department
in 2008 concluded that the Russian leader may have Asperger's Syndrome, a type of high-functioning autism. The report said it may account for his apparently high degree of control.
A Pentagon spokesman said there was no guidance from the Department of Defense on the report and experts told CNN they were skeptical of the reliability of the Asperger's claim.
For the record, the Kremlin has dismissed the allegation as utter nonsense.
Putin, though, is an enigma.
His unflinching support for rebel separatists in Eastern Ukraine, despite their alleged excesses, has plunged Russia's relations with the West into their worst crisis since the end of the Cold War.
Even in the face of mounting international sanctions that have isolated Russia and helped hobble its fragile economy, Western officials say weapons and manpower continue to flow across the border, although the Kremlin insists it is supplying neither.
Clearly, Putin is determined to get his way in Ukraine.
We already know, essentially, what this means in terms of a peace deal -- a truce was signed last September, although it didn't hold.
The Minsk Protocol agreed that, among other things, autonomy would be granted to Ukraine's southeastern regions. The Russian language would be given official status. A buffer zone would be established along the front lines and heavy weapons would be pulled back from civilian areas.
But Putin may actually want much more.
On an official visit to Egypt this week, the Russian president dropped a large hint -- and not for the first time.
In an interview with the Al-Ahram newspaper
he rejected Russian responsibility for the crisis in Ukraine.
"It emerged in response to the attempts of the U.S.A. and its Western allies, who considered themselves winners of the Cold War, to impose their will everywhere," Putin told the newspaper.
"Promises of non-expansion of the NATO to the east have turned out to be hollow statements," he said.
A solution to the Ukraine crisis, then, may involve ruling the country out of any future NATO membership, however unpalatable that may be to some in the West.
Russian diplomats call it guaranteeing Ukraine's "neutral status" -- which sounds much better than "capitulation."
The bigger problem, though, is that this may not end with Ukraine.
For Putin, this crisis is only the latest in a catalog of grievances, which includes the West trampling over Russia's interests from Kosovo to Iraq, to Libya and Syria.
Putin's ultimate goal may be to tear up the post-Soviet assumptions about what Russia will tolerate, and permanently change Russia's relationship with the West.