The commentary gives four groups of quality:
1. Sensible qualities — such as heat, cold and color.
2. Psychic qualities — such as knowledge and traits of character.
3. Qualities associated with quantities — such as forms or shapes.
4. Dispositional qualities — capacities to receive or resist an effect.
All concern what something is like. A quality may still be measured numerically; that use of numbers does not automatically turn the quality itself into the category of quantity.