Suppose I say I was influenced by Ernest Hemingway’s books. If I’m an aspiring novelist, I probably mean this in the formal/practical sense: I want to write novels like his, and will probably turn out a lot of painful stuff full of terse declarative sentences. But I might have a more substantive influence in mind: I’ve adopted a particular kind of vision of masculine virtues with a premium on physical courage, “grace under pressure” and so on. Where that falls on the theoretical/practical dimension depends on whether I actually take up bullfighting or enlist in someone else’s civil war.This is in part what I found dissatisfying about many of these lists and something of what I was getting at when I expressed skepticism about so many of the books being high-minded works of philosophy that the bloggers encountered in college or even graduate school. I'm not usually interested in learning when and how someone adopted a particular belief. You can usually determine the content of a blogger's important beliefs without recourse to a book list with biographical descriptive interludes. Even the "habit of thought" distinction is not really that interesting, as those are also fairly evident from reading the blog in question. Has "learning to think like a lawyer" (perhaps the most well-known "habit of thought") really influenced me? Am I a different person now than I was before law school? What I do is not necessarily who I am. And influence in the substantive/practical sense can also be somewhat dull, unless the blogger's personal history is particularly interesting to you.
The theoretical/practical dimension is especially fuzzy for writers and academics, for whom there’s not as clear a division between “what you think” and “what you do.” But even for us, I think there’s a rough distinction between adopting a belief and adopting a habit of thought.
What's most revelatory about some of these lists is seeing what books formed the character of the person writing. I think your character is unlikely to change dramatically after a certain age, and even with the content of your views. What speaks to you? The idea that influences consist chiefly of books that taught a mature you some mechanistic system for analyzing the world is somehow impoverished. There was a you who selected that book in the first place. Who is he?