Conversation so far:
What does language have to do with Maurice Merleau-Ponty?
The work dealing mainly with language for Maurice Merleau-Ponty begins with the reflection on artistic expression in his book The Structure of Behavior.
What did Maurice Merleau-Ponty write in The Structure of Behavior?
The Structure of Behavior contains a passage on El Greco that prefigures the remarks that Maurice Merleau-Ponty develops in Cézanne's Doubt and follows the discussion in Phenomenology of Perception.
Was Maurice Merleau-Ponty's book, The Structure of Behavior, a best seller?

Question: what was his greatest accomplishment?
Self-contained rewrite: What was Maurice Merleau-Ponty's greatest accomplishment?