Thus the behaviour of the sense-data which represent the cat to me, though it seems quite natural when regarded as an expression of hunger, becomes utterly inexplicable when regarded as mere movements and changes of patches of colour, which are as incapable of hunger as a triangle is of playing football.
[Problems of philosophy, Bertrand Russell, Chapter II]
What does "a triangle if of playing football" mean? How could I understand that expression? I think it means "a triangle is incapable of playing football". Is it right?