Full Idea
The essential difference between persons and other creatures is in the structure of the will, with their peculiar characteristic of being able to form 'second-order desires'.
Clarification
'Second-order desires' are desires about desires
Gist of Idea
Persons are distinguished by a capacity for second-order desires
Source
Harry G. Frankfurt (Freedom of the Will and concept of a person [1971], Intro)
Book Reference
'Free Will', ed/tr. Watson,Gary [OUP 1982], p.82
A Reaction
There are problems with this - notably that all strategies of this kind just shift the problem up to the next order, without solving it - but this still strikes me as a very promising line of thinking when trying to understand ourselves. See Idea 9266.
Related Idea
Idea 9266 A person essentially has second-order volitions, and not just second-order desires [Frankfurt]