Capacity is a question of internal chemistry, modifiable by injury, disease, accident, shock, exhaustion.
"The Glands Regulating Personality"
Louis Berman, M.D.
Sounds, while subtle, refined, and easily modifiable, are transitory.
"How We Think"
John Dewey
The division of rights would naturally follow the division of duties and functions; and that is already made by consent, or at all events not by law, but by general custom, modified and modifiable at the pleasure of the persons concerned.
"The Subjection of Women"
John Stuart Mill