the failings of biographers

In this interview, C. S. Lewis’s stepson Douglas Gresham reveals facts about his upbringing, and especially about his brother David, that he has kept secret for more than half a century:

For decades, despite a booming cottage industry of Lewis biographies and endless academic theorizing about the last years of Lewis’s life, Douglas kept to himself the fact that Lewis struggled mightily to help his mentally ill stepson. “We didn’t tell anybody,” he told me. “The only reason I’m releasing it now is because people should know what Jack put up with and what Warnie put up with and how heroic they were to do it at all.” It is time, he added, “that people understand what Jack and Warnie went through. Jack and Warnie didn’t know what the heck to do.”

Gresham tells more harrowing tales, and then at the end we get this:

“Nobody seems to know that David was ever there,” Gresham told me. “He seems to have faded out of existence… the biographies that I’ve encountered about Jack, for example, hardly mention my brother.” For Gresham, it’s a signal that the biographers haven’t dug deep enough.

So the biographers haven’t dug deep enough to discover … what Gresham himself has made a special point of keeping hidden all these years, including in his own memoir of his years in Lewis’s house. What does he think we should have done, tied him down and administered truth serum? Threatened him at gunpoint? (I set aside the question of whether biographers of C. S. Lewis are obliged also to be biographers of David Gresham.)