Yeah well, ya know, that's just, like uh, your opinion, man. But seriously, I don't see the movie like that, or at least not to the same degree. It's a play on mid-century hardboiled detective stories (notably Chandler's Marlowe), which I'm a big fan of. So, by its nature, all those involved in the case have to be looked at skeptically until the pieces start to make sense. But it's not impossible to know what to believe, as it becomes clearer as the case moves towards its resolution. The characters are not all unreliable.

Maude becomes a semi-trusted ally, enabling the breakthrough that solves the case. How commended an artist she may or may not be isn't really important. While pushed away, Da Fino also seems like a believable would-be ally and a source of useful information to the Dude in the case.

The Big Lebowski, and possibly Brandt as his associate, are the least reliable as they're driving the deception at the heart of the case. The Big Lebowski used Bunny's disappearance for a money con, but there’s no reason to think his story about his legs couldn’t be believed. If he was going around lying about such a fundamental thing, there’s every reason to believe that it would have been exposed during his public, commended life or by Maude.

The nihilists are also guilty of carrying out a deception. But beyond that, what we see of them as characters and their role in the story seems quite believable. The directors choose to show us the scene of the girlfriend’s missing toe to make it clear to us what has happened there.

Might Jackie have tried to squeeze Lebowski harder? Possibly. But fundamentally, Jackie’s core claim does not seem to be in doubt that Bunny owed money. The Big Lebowski doesn’t want to honour her debts (and maybe can’t if Maude controls his money), but he doesn’t dispute that Bunny would owe money.

I don’t see any reason to doubt that it was the Larry they were looking for. They found his homework and tracked him back. If it was a complete mistaken identity, surely any kid with nothing to hide would have said something (ie, protested that it wasn’t his homework). It’s more likely that he was indeed a lightly supervised little prick, who might steal a car to joyride in, and as such was stonewalling them.

Besides the deliberately deceptive Big Lebowski and Brandt, Walter is probably the most unreliable character. But that’s just because of Walter being Walter. Could he have made up the story about Jesus? Sure, possibly. But I don’t see a need to make that stretch.

Like the nihilists’ girlfriend’s toe scene, that the directors chose to show us Jesus going door to door, rather than just leaving it as hearsay from Walter, gives me confidence that it’s true. It also makes for a more compelling character, so I don’t see any benefit in undermining that. Jesus isn’t part of the case, so there’s no need to make him a character whose backstory should be doubted.

Beyond that, though not part of the case, other characters in the film seem straightforward and believable: Donny, Smokey, Marty, the Stranger-- aw, look at me, I'm ramblin' again. In short, beyond the mystery and deceptions in the case, inherent to the detective story genre, I don’t see the film as having an overarching core theme that it’s impossible to know what to believe.