Full Idea
The existence of a material thing is defined in terms of the actual and possible occurrence of the sense-contents which constitute it as a logical construction.
Gist of Idea
Material things are constructions from actual and possible occurrences of sense-contents
Source
A.J. Ayer (Language,Truth and Logic [1936], Ch.7)
Book Reference
Ayer,A.J.: 'Language, Truth and Logic' [Penguin 1974], p.162
A Reaction
Obviously we need 'possible' experiences so that unperceived trees can still exist, but it is a can of worms. Is speculation about a possible world an account of possible experiences? Realists want to know WHY we think certain experiences are possible.