The movie creates a surreal vision of a bygone Southern California dense with smog and reeking of marijuana, when every street seemed to have its own massage parlor. The atmosphere is so steeped in vintage psychedelia that it is impossible to distinguish reality from fantasy; it could all be a dream. The best approach to “Inherent Vice” is not to look for profundity but to lie back, inhale imaginary clouds of secondhand pot smoke, and go with the flow of a yarn so amusingly convoluted it makes “The Big Sleep” feel like children’s bedtime reading.