1. What is the mind’s physical basis?  We know the answer since a long time: 
    
    > The mind’s physical basis is the brain.
    
       But that’s not the real issue. The real problem is:   

    > How does the *mind* work?

2. One may use as a working definition:    

   > The mind are the mental processes of the brain.

   These processes constitute the human data processing to construct information. This information controls how the person behaves and acts as an agent. 

3. The details are researched by neuroscience and cognitive psychology - but not by musing about metaphors from Heraclitus or about etymology like Heidegger did.

4. **Added** in reply to a comment: The subjective method of observing the mind at work is introspection. One may introspect those mental processes which are conscious.