When I'd been a cadet, one term, we'd studied (among much else) a play by Shaw and a tragedy by Shakespeare. Shaw's plays had a clear message, explained importantly in the preface to each. One may question if early experience influenced his writing to a very great extent. Did Shakespeare have a message or were his works coloured by childhood traumas? Could he not have just written to earn a living in the then world of entertainment? Of course, all actions and imaginations by everyone are influenced by their experiences to a greater or lesser extent. However, could it be that we may assign an undue importance to these? Certainly, please inform Mr John Gray that his thesis in this case tends to convince one of its validity.
What does the bold part mean?
Isn't "convince" always followed by somebody rather than something? How can sb/sth convince sth else?