Compare with Hegel, who stipulated "thought thinking itself" as the foundation of his "System to end all systems." Which implies there is no "something" outside immediate personal consciousness worth thinking about; so just get rid of it all, the entire "exterior world," and take the fast lane to the Absolute Idea...which seems to be indistinguishable from the Self...which (somewhat ironically) has been rendered a total abstraction by means of this process.
Compared to Hegel, Descartes is an empiricist.
Hear, hear.
This is funnier than your teacher's joke.