I want my father to be just my father, the way he has always been, not a separate person with an earlier, mythological life of his own. Knowing too much about other people puts you in their power, they have a claim on you, you are forced to understand their reasons for doing things and then you are weakened.
The quote from Margaret Atwood's "Cat's Eye" expresses a desire for a simple and uncomplicated relationship between the speaker and her father. She longs for him to remain the father she has always known, rather than becoming a complex figure with a mysterious past. This wish reflects a wish for familial ties to stay pure and unblemished by deeper, potentially troubling knowledge about individuals we care about.
Moreover, the quote suggests that knowledge about others can create a sense of obligation and vulnerability. By understanding the complexities of another person, one may feel burdened by their past and choices. This notion implies that intimate relationships can become complicated when we uncover too much about the people we love, potentially leading to a loss of personal power and autonomy.