首楞嚴義疏注經 3.144

3.144

共成一體破也。初四句正破，若頭與手共生一觸，遂令二種合為一體。設許一體，觸自不成，此結破也。

Refuting through their jointly forming a single substance. The first four lines are the direct refutation: if head and hand together produced a single touch, this would cause the two to merge into a single substance. Even granting a single substance, touch itself would not be accomplished; this concludes the refutation.