Full Idea
We may lay down the following definition: Physical things are those series of appearances whose matter obeys the laws of physics.
Gist of Idea
Physical things are series of appearances whose matter obeys physical laws
Source
Bertrand Russell (The Relation of Sense-Data to Physics [1914], §XI)
Book Reference
Russell,Bertrand: 'Mysticism and Logic' [Unwin 1989], p.165
A Reaction
We will then have to define the laws of physic without making any reference to 'physical things'. There is an obvious suspicion of circularity somewhere here. I find it very odd to define objects just in terms of their appearances.