The case study of Mary Northern illustrates that an individual may have decision$-$making capacity in some matters while lacking decision$-$making capacity in other matters. Allen Buchanan and Dan Brock make a similar observation when they say that decision$-$making capacity $--$

$$ Can be judged perfectly and without controversy

$$ Involves patient feedback and response

Requires the capacity for reasoning and deliberation

$$ Can be partial or a matter of degree

Is decision$-$relative