首楞嚴義疏注經 3.91

3.91

處以生門為義，六根、六境是識生處，根已前破，今正破境，然亦以根相對而破，故雙問色生眼生等也。

'Base' takes 'door of arising' as its meaning; the six faculties and six objects are the places where consciousness arises. The faculties have already been refuted previously; now the objects are directly refuted, yet they are also refuted in mutual opposition to the faculties; therefore it asks both whether form produces or the eye produces, and so forth.