The 'Jonses' actor - who has daughter Madelaine, 11, and seven-year-old son Kyd with wife Tea Leoni - admits he often thinks about completing his doctorate in comparative literature, but has accepted it is unlikely to ever happen. David - who left Yale University without completing his thesis - said: "My career started, so I couldn't afford the time to finish it, but I do retain an academic interest in literature. "Actually, I have an interest in finishing my PhD, but I just know I never will. It's like if I almost became a surgeon - that doesn't mean I am going to operate on anybody right now." As well as being an avid reader, David, 49, has been working on a script for a movie, but after accepting it will be a struggle to get his work onto the big screen, is now considering turning it into a novel instead. He added to the Sunday Times newspaper: "I have things in mind for writing and directing, but the scripts I write seem to fall into this independent world which I started veering towards as I was finishing 'The X Files', about 10 years ago. "And it is a hard world right now, when you want to make the kind of movies I am writing. I think they could be popular, and could do business, but it's hard to prove that at the script stage. At some point, I think somebody is going to take a chance and give me some money to make one. "I have been working on this script this past winter, and I think it is quite dense. I don't know if it is a movie or not. I hope it is, but I am also going to turn it into a novel, just in case."