Full Idea
A concern for happiness is the unavoidable concomitant of consciousness; that which is conscious of pleasure and pain, desiring that that self that is conscious should be happy.
Gist of Idea
A concern for happiness is the inevitable result of consciousness
Source
John Locke (Essay Conc Human Understanding (2nd Ed) [1694], 2.27.26)
Book Reference
Locke,John: 'Essay Concerning Human Understanding', ed/tr. Nidditch,P.H. [OUP 1979], p.346
A Reaction
It is an interesting question whether a being would be concerned with 'happiness' if they were conscious thinkers, but lacking pleasure and pain. Presumably they would desire eudaimonia - that their life go well, in some way.