One of the first european artists to practice and theorize totally abstract (that is, totally non-representational) art was:

One of the first European artists to practice and theorize totally abstract (that is, totally non-representational) art was "Wassily Kandinsky".

Explanation:

Wassily Wassilyevich Kandinsky, a Russian painter and an art theoretician. Kandinsky is widely regarded as a pioneer to the abstract art. Kandinsky created abstract works based on his artistic experience, long intense thinking and maturity.

He mentioned this devotion towards inner beauty, enthusiasm and inner need for spiritual desire. This was a key aspects of his art. The Blue Rider collection is a large, expressive mass of colours that are valued regardless of shape and line; they are no longer used for demarcation, but as a free complement to images of extraordinary power.

c. gabriele was a catholic priest while also being a composer.

ive noticed that too but is this a question