Purity = objective. Quality = subjective. Usability at some point.
This may help. jt
Q. In a democratic society, how important are elections?
A. Very important. Sex can only happen when a male gets an election.
"March on. Do not tarry. To go forward is to move toward perfection. March on, and fear not the thorns, or the sharp stones on life's path." -- Kahlil Gibran