Full Idea
One and the same thing can, at the same time, be good and bad, and also indifferent. For example, music is good for one who is melancholy, bad for one who is mourning, and neither good nor bad to one who is deaf.
Gist of Idea
Music is good for a melancholic, bad for a mourner, and indifferent to the deaf
Source
Baruch de Spinoza (The Ethics [1675], IV Pref)
Book Reference
Spinoza,Benedict de: 'Ethics', ed/tr. Curley,Edwin [Penguin 1996], p.115
A Reaction
This sounds neat and obvious, but both the mourner and the deaf person might well acknowledge that music is a good thing, while failing to appreciate it at the time. I accept that a concert was good, even if I didn't attend it.