An ambitious book indeed. Churchland covers a host of issues—philosophy of language, epistemology, mind, and science. The book is rather dense and a slow read.
His general conclusion is that observation is heavily theory laden and, moreover, those theories can be wrong. A better scientific understanding can be achieved if (and he thinks, when) a scientific language replaces our current conceptual framework.
Inside this broader argument, he has a wonderful critique and replacement of the synthetic/analytic distinction. He plots theories and ideas on a grid with the vertical access as “semantic importance” and the horizontal as “systemic importance”—the former being the importance of the term or theory's meaning in relation to the other instances of that term's use, and the later being a term or theory’s importance in the broader linguistic scheme. The more north and east the plot, the more engrained the term or theory.
All things considered, a wonderful little philosophy book.