Full Idea
Some have argued that a mereological whole should not be identified with the sum of its parts on the grounds that the former possess certain properties - specifically modal and (perhaps) counterfactual properties - that the latter lacks.
Clarification
'Modal' concerns necessity; counterfactuals concern what-if situations
Gist of Idea
It is argued that wholes possess modal and counterfactual properties that parts lack
Source
Mark Rowlands (Externalism [2003], Ch.2)
Book Reference
Rowlands,Mark: 'Externalism' [Acumen 2003], p.14
A Reaction
I am not convinced that modal and counterfactual claims should count as properties. If my pen is heated it melts (a property), but if my pen were intelligent it could do philosophy. Intelligence is a property, but the situation isn't.