Taken literally, this phrase could be the stuff of nightmares. A pulsing brain, throbbing along independently of a body, like some kind of parasitic metronome… But thankfully, Ellen's dad uses this phrase as a metaphor to express the value of individuality:
Geeky is one of Dad's favorite words, and I listen with glee to my brother's imitation of our father: "Geeky people often have that which is most valuable in this life." Link pauses here for effect, so that James and I can join in, shouting Dad's favorite phrase, "A mind with its own heartbeat!"
This appreciation for the person who marches to the beat of a different drummer is a running theme throughout My Heartbeat. (See that? It's even the title of the book). And it's not just about valuing differences; it's about knowing yourself well enough to understand what makes you different. You can't be true to yourself unless you firmly know who you are.
Discovering her mind's own heartbeat becomes something of an obsession for Ellen, which isn't strange given her age and all the issues her family is confronting. Mostly, though, she doesn't want to disappoint her father, who holds this quality to be extremely important:
The thing about Dad is that he makes you want and dread his attention at the same time. I like the fact that he's interested in my thoughts, but I'm always terrified of what he thinks about what I think. After all, I know he's judging whether or not my mind has any kind of a heartbeat yet. What can I safely say about what I thought? (3.21)
It's a bit sad that she's more worried about her father judging her mind's heartbeat than just discovering what it is for herself, but she admires her dad so much that to disappoint him would be tantamount to failure.
Here's where things go a bit sour, though: Ellen's dad, the paragon of intellectual prowess (according to him, at least), pays a lot of lip service to treasuring individuality, and yet does everything he can to repress his son's search for his sexual identity. That makes him a pretty big hypocrite, right? If Link's mind's heartbeat is telling him that he loves James, shouldn't he listen to it?
And that right there, folks, is the crux of the issue. Sometimes even the most educated, well-meaning people can have prejudicial thoughts that override their good intentions. Even though their dad thinks he's been a vocal proponent of his kids finding themselves, he can't help but have deep-seated issues with homosexuality. Eradicating these preconceptions is part of what the gay rights movement is all about.
Ultimately, Ellen finally realizes that she may never fully understand how her father's mind works:
"What is this about?" I ask Dad one night, picking up volume two. It is so long I cannot imagine that there is an end that can be described as either happy or true.
"A lost world," he says. "A life just out of reach."
This is fitting, since I think his finishing it will remain forever out of reach. I would venture that its length and difficulty are why he is reading it in the first place. But of course I don't know if that is, in fact, true. Dad learned French, Latin, and Italian in college, but he taught himself German. Was it to read this book? Why not read a three-volume book in French? I leave the study. Suppose he answered all my questions. I still wouldn't discover what the quality is of his mind's heartbeat. Which is what I am really asking with my questions about his reading habits. (17.44)
So, even though she can't quite get the measure of her dad's mind's heartbeat, (maybe because he doesn't know it, himself) Ellen ends the book knowing more about her own:
It will be amazing in the way that girl walking through the park is. I see her in her hideous green skirt, acting as if her mind isn't beating with what her body knows. Although I'm still in the process of meeting her, I've already decided to like her.
Not because she's curious, careful, kind and intense. But because she's let somebody else discover that about her and love her for it. (20.58-59)
Looks like our main girl is learning how to walk to the beat of her own heart.