According to the author, imagining the loss of a sense is the only way to make people value and actually use what they have.
She notices that human beings take for granted whatever they have always had, and pay attention only to what they might lose: “use your eyes as if tomorrow you would be stricken blind.” The imagined loss works like a deadline — it turns an ordinary day into the last day, and a person suddenly looks properly.
She then applies the same method to every sense: “Hear the music of voice, the song of a bird, the mighty strains of an orchestra, as if you would be stricken deaf tomorrow. Touch each object as if tomorrow your tactile sense would fail. Smell the perfume of flowers, taste with relish each morsel, as if tomorrow you could never smell and taste again.”
Why it happens: Coming from Helen Keller, this is not a clever idea but a report. She is describing what her own loss taught her, and offering it to us so that we need not learn it the hard way.