The history of the world may be the history of class struggle, but the history of class struggle — at least the decisive chapter chronicled in “The Young Karl Marx” — turns out to be a buddy movie. Marx (August Diehl), a scruffy journalist, and his sidekick Friedrich Engels (Stefan Konarske), a renegade rich kid, meet in Cologne, Germany, in 1844 and overcome some initial wariness by bonding over their shared contempt for the Young Hegelians. (Man, those guys are lame.) They set out to write a “Critique of Critical Criticism,” and when it’s published (as “The Holy Family”), it’s something of a hit. By the time the revolutions of 1848 are ready to happen, Marx and Engels are the Mick Jagger and Keith Richards of the European left, rock stars for an age of revolution.

Scrupulously faithful to the biographical record, “The Young Karl Marx,” directed by Raoul Peck (from a script he wrote with Pascal Bonitzer), is both intellectually serious and engagingly free-spirited. The founders of Communism, full of intensity and ambition and sporting contrasting beards, look and act like pioneers of brocialism. They spend some drunken evenings hashing out the labor theory of value — Engels holds his liquor better than Marx — and many hours, together and separately, in furious paroxysms of thought.

Thinking notoriously resists being captured on film, and Mr. Peck often falls back on its most common analogues, scribbling and smoking. Marx in particular does a lot of those things. But Mr. Diehl’s performance is a marvel of itchy intelligence, and it strips away almost all of the character’s accumulated importance. “The tradition of all dead generations weighs like a nightmare on the brains of the living,” a slightly older Marx wrote, and what is most remarkable, indeed most exciting, about “The Young Marx” is how lightly that burden rests upon it.