He explains how as the film was growing, he didn't know exactly what it meant. He didn't understand how all the individual sequences came together as a whole. So he started reading his Bible, and "One day I read a sentence and that was it. I saw the thing as a whole." Somewhere in the Bible is a sentence that for David Lynch fulfills the vision of Eraserhead.
I can actually relate to that method. And it resonates a bit with how the band
Garbage originally wrote their songs. Members would contribute scraps of ideas or sentences (a pile of "garbage") and then Shirley would patchwork them together into a sensible or half-sensible lyric.
Apart from adaptations like
Dune and maybe a TV show like
Twin Peaks, that might often be it. Where Lynch is akin to a sculptor who looks at a pile of miscellaneous junk collected in the backyard and wonders what sort of coherency could be concocted from it. Accordingly, the significance rarely revolves around a trendy social or psychological enlightenment that the typical art film molds its metaphors around. But instead whatever discovery/principle he finally comes across that will unite and organize the loosely associated scenes.
The first part of "Mulholland Drive" started out as a failed pilot for a television series, and he completely changed what it concerned in order to turn it into a movie (granting that the former itself had even had a pre-planned destination).
This haphazard approach might even have longer legs than -- again -- an intellectual flick symbolizing a moral or political message. Since the latter can potentially become dated if it pertains to a specific angst or fixation of an era, rather than a more eternal or timeless issue.