I wonder if this film was made as an intentional imitation of or tribute to Andrei Tarkovsky's Andrei Rublev, with the basic premise of having a famous artist as a witness to society as a whole? The scenes with the Spanish Inquisition remind of those with the Mongol Horde, with Rublev vs. Brueghel as witnesses.
shareThere are strong parallels, structurally and aesthetically, and in the dominant theme being the impotence of virtuous men in the face of organised evil.
In Andrei Rublev, the dominant idea being conveyed, as I perceived it, was the dignity of the act of creation in and of itself - whether it's painting icons or casting a bell or composing a ribald song mocking the boyars, art and craft are ultimately more meaningful than religion and don't necessarily have to achieve anything for wider society in order to justify themselves.
In The Mill and The Cross, the theme that comes across more strongly is the duty of the artist to bear witness to suffering and injustice, and to document it - it is the importance of art as protest rather than just as an end in itself. However, the film seems almost equally pessimistic about the prospect of art being able to bring political change. Perhaps another way of looking at it, is that it is about the artist's potential to create his or her own reality, which then becomes as real as the external reality.
"People don't go to the movies to be depressed - that's what the theatre's for!"