法華義疏 9.251

9.251

初云說外道，而外道十八大經復無此說，故是自作，但既非內教，理同外道也。

At first it was called expounding non-Buddhist [treatises], yet the eighteen great scriptures of the non-Buddhists do not have this teaching; thus it was made by themselves. But since it is not the internal teaching [of Buddhism], in principle it is the same as non-Buddhist teachings.