There’s a world of knowledge out there and it all intertwines. The study of any one subject begins to touch on the boundaries of others, motivating study into the new subject. When reading and when writing, we learn new things, which could lead to feelings of treading on unfamiliar ground.
I’ve met some brilliant and hard-working people in my life in academia. I’ve met people who read articles by the bushel and books by the shelf, but I’ve never met one who had read everything worth reading. There’s too much knowledge out there for any one person to know everything there is to know and to read everything that has been written. And, of course, we recognize this; it is the motivation behind the specialization all around us. Nonetheless, it is not unusual to become paralyzed by the sense that we don’t know enough.