Full Idea
Readers of Locke have been wrong to imagine that primary qualities are not themselves powers.
Clarification
'Powers' initiate causal sequences
Gist of Idea
In Locke, the primary qualities are also powers
Source
report of John Locke (Essay Conc Human Understanding (2nd Ed) [1694], 2.08.15) by John Heil - From an Ontological Point of View 17.2
Book Reference
Heil,John: 'From an Ontological Point of View' [OUP 2005], p.197
A Reaction
This is part of the move to connect Locke with modern essentialism about natural laws. If a disposition is a power, then clearly being hard or square will affect the dispositions, and hence be a power. Secondary qualities result from powers.