You can know a thing to death and be for all purposes completely ignorant of it. A man can know his father, or his son, and there might still be nothing between them but loyalty and love and mutual incomprehension.
The quote from Marilynne Robinson's "Gilead" highlights the complexity of human relationships and the limitations of knowledge. One can possess extensive information about someone, such as a family member, yet still lack true understanding of their inner feelings, thoughts, or motivations. This suggests that mere factual knowledge does not equate to genuine connection or comprehension.
Additionally, the emphasis on loyalty and love in the quote indicates that while these emotions can forge strong bonds, they may not bridge the gap of mutual understanding. The relationship between individuals, even those close to each other, can sometimes be marked by a profound sense of incomprehension despite their emotional ties, illustrating the intricate nature of human connections.