Does "define an individual" mean "determine the essential quality of an individual"?

Background info:

Saks lives with schizophrenia and has written about her experience with the illness in her award-winning best-selling autobiography, The Center Cannot Hold: My Journey Through Madness published by Hyperion Books in 2007.[6] Saks is also a cancer survivor. She emphasizes that "illness of any kind need not define an individual, while remarking on the different ways that mental and physical illnesses are regarded".[7]
I would say that it means that the individual is not the disease. Some people equate a debilitating mental disorder with the person who has it.
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Who's "remarking on the different ways"? The author Saks?
SweetFreedom Who's "remarking on the different ways"? The author Saks?