首楞嚴義疏注經 3.128

3.128

Refuting its being born from the faculty. The first part introduces [the assertion]; 'in your [mouth]' directly refutes that one tongue could not know multiple flavors. If flavor conforms to the tongue, flavors should not be distinct. From 'if it does not' onward is a conditional refutation: supposing you grant that flavors are not distinct, then since flavors are undifferentiated, how does that constitute knowing flavor? From 'if it shifts' onward refutes the shifting of flavor, [showing that] the tongue should be multiple in substance; the first two lines refute through the contrary, and the latter two lines conclude the refutation. This means that if the tongue conformed to flavors, the tongue would become multiple; but in your case it is not so, hence it says: 'how could multiple flavors be known by a single tongue?'