Georg Wilhelm Friedrich Hegel wrote the *Phenomenology of Spirit* in Jena in 1806, as Napoleon's troops entered the city — he is said to have finished the preface to the sound of French artillery. Published in 1807, the work is one of the most difficult and influential books of modern philosophy.

Hegel's basic move is this: consciousness is not a fixed subject but a movement that advances by working through its own internal contradictions. The book begins with 'sense-certainty' — the simplest 'this, now, here' knowledge — and moves through perception, the understanding, self-consciousness, reason, Spirit (Geist), religion, and finally absolute knowledge, each stage falling into contradiction with itself and 'lifting' (Aufhebung) into a more comprehensive position.

The most famous section is the 'master and slave' dialectic. Two self-consciousnesses confront each other for mutual recognition; the one who clings to life and the one who risks death turn the relation into a master-slave hierarchy. But in Hegel's paradoxical thesis, the slave's labour eventually makes him more independent than the master — because the slave alone touches the world. Marx will build his thesis on labour and freedom directly out of this passage.

Hegel's 'Spirit' is not individual mind but collective reason realising itself through history. History has a direction — for Hegel, the spread of the consciousness of freedom. These theses forced the whole of 19th-century philosophy — right, left, existentialist, pragmatist — to reckon with Hegel in one form or another.