Gilroy begins with a complaint about cultural studies. Its English formation borrowed from wider European traditions of thinking about culture in which racialised others figure only as things to be known and criticised, and its own histories seldom register how much they already owe to black cultural theory and to figures such as C. L. R. James and Stuart Hall. The motive he states for writing is to have black people recognised as agents with minds and an intellectual history.

Against nationalism and ethnic absolutism on every side -- the belief in cultural purity, the picture of black Britain as two intact communities colliding -- he offers units of analysis lodged between the local and the global, chief among them diaspora.

The ship is his organising figure: not an emblem of the triangular trade but a moving site of dissent and cultural production that links ports, recalls the middle passage, and unsettles where modernity is thought to begin.