Full Idea
A pure quality, a property altogether lacking in dispositionality, would be undetectable and would, in one obvious sense, make no difference to its possessor.
Gist of Idea
If properties were qualities without dispositions, they would be undetectable
Source
John Heil (From an Ontological Point of View [2003], 11.4)
Book Reference
Heil,John: 'From an Ontological Point of View' [OUP 2005], p.118
A Reaction
This seems to be a very forceful and simple reason why we cannot view properties simply as qualities of things. Heil wants properties to be dispositions and qualities; personally I would vote for them just being dispositions or powers.