Was PKD Possessed by the Kabbalist Abulafia?

[TO CHARLES N. BROWN, Locus]
Dear Charles,
April 23, 1979
This is to let you know that after four years of research and work I have
finally finished my new novel VALIS for Bantam. In the writing I collaborated
with the spirit of the 13th century Jewish Kabbalist Abraham ben Samuel
Abulafia who seizes control of me from time to time, as circumstances require.
Hope all is well with you.
Cordially,
Philip K Dick

The Selected Letters of Philip K. Dick 1978-1979 p.225