Martin Heidegger (1889–1976) never studied Chan Buddhism. He read a few books on Zen, corresponded briefly with D.T. Suzuki, and was reportedly intrigued but noncommittal.
And yet, his philosophy resonates with Chan in ways that are almost uncanny.
Gelassenheit: Releasement
In his later work, Heidegger used the medieval German word Gelassenheit — releasement, letting-be. It describes a mode of thinking that doesn't grasp or control, but lets things show themselves as they are.
Chan has a word for this: wú niàn (無念) — no-thought. Not the absence of thinking, but the absence of grasping at thoughts. Letting them arise and pass, like clouds in an empty sky.
Lichtung: The Clearing
Heidegger's Lichtung — the clearing — is the open space in which things can appear. It's not a place; it's the condition for the appearance of places.
Chan's concept of kōng (空, emptiness) works the same way. Emptiness isn't nothingness. It's the spaciousness that allows everything to be.
The Shared Insight
Both Heidegger and Chan point to the same problem: the Western philosophical tradition (and much of Buddhist scholasticism) has forgotten the ground of thinking. We study objects but forget the awareness in which objects appear.
Heidegger called this forgetting Seinsvergessenheit — the forgetting of Being. Chan calls it wú míng (無明) — fundamental ignorance.
The Difference
Here's where they part: Heidegger wrote about the clearing. Chan practitioners sit in it.