成唯識論述記 4.903

4.903

述曰：意識與七同緣、不緣皆定依故。若與五同緣，亦依五識，如前教證。

[The Commentary states:] This is because the mental consciousness definitely relies on the seventh whether it cognizes the same object as it or not. If it cognizes the same object as the five [sensory consciousnesses], it also relies on the five consciousnesses, as in the previous scriptural proofs.