What remains is the basic idea that representations in general are to be constructed by parabolic induction of cuspidal representations. A similar philosophy was enunciated by Israel Gelfand, and the philosophy is a precursor of the Langlands program.
The essential notion that remains is that representations in general are developed through parabolic induction of cuspidal representations. A comparable idea was proposed by Israel Gelfand, and this philosophical framework serves as an antecedent to the Langlands program.