It's a little odd, watching a movie you've been looking forward to in one capacity or another and finding yourself slightly disappointed. It's not that this is bad by any means, but despite a marvelous premise, it's much better in the broad strokes of the plot than in the details that constitute that plot. It lands on the intended emotional beats, but imperfectly in light of how the narrative effectively comes across as seesaws tipping back and forth on a single fulcrum rather than the following of a path - a sense that's particularly odd since there are discernible progressions for characters and the story at large. 'L'idiot' is enjoyable, but less than wholly captivating or essential.
This is quite well made, to be sure. Georges Lampin shows a deft hand in orchestrating shots and scenes as director; I believe the cast give excellent performances, not least Gérard Philipe as the gentle prince and Edwige Feuillère as fiery Nastasia. While the original music of V. De Butzow and Maurice Thiriet mostly sticks to the background, at select moments it rears its head with ponderous dramatic themes that are rich and enticing. Those behind the scenes turned in fine work all around, with super costume design, hair, and makeup, and terrific production design and art direction adjoining lovely filming locations. Though not specifically striking, the cinematography and editing are splendid, and in all other regards the picture is broadly well done.
I'm a little stuck on the writing, however. In the wide strokes there's much to love here in the tale of a kind, innocent, somewhat naive man being considered altogether mad amidst the less virtuous goings-on of the figures and world around him, and the unwitting effect that his goodness will have on others for good and for ill. Indeed, the people around him think too much or too little of how he presents, and make assumptions; drama invariably ensues, swirling foremost around assertive, beleaguered Nastasia. Would that the screenplay were fleshed out more, however, to make the push and pull of others' behavior more meaningful than what feels like a child's game of picking petals off a flower (e.g. "He loves me, he loves me not") and putting into motion whatever dichotomous statement arbitrarily comes up last. The sketch is already there, and it needed only to have been developed into a more complete image. Moreover, for as much as the prince's name comes up as having (unintentionally) caused such havoc, he's not in the feature as much as one might suppose without any foreknowledge, and the connections between him and the characters who have had their outlooks altered come across as a tad flimsy.
I do actually like 'L'idiot,' and I think it's worth watching. Despite strong acting and craftsmanship, however, storytelling that is less than 100% convincing results in division of one's attention. What strengths this film can claim are not so grabbing as to help it to especially stand out, so at length the viewing experience is one that's satisfying and entertaining, but maybe not as much as one might hope from cinema. Do watch this 1946 movie, and perhaps you'll find it a more fulfilling experience than I have. Don't necessarily go out of your way for it, though, and don't expect a revelation.
