| Quote #1
—you have all, I dare say, heard of the animal spirits, as how they are transfused from father to son, &c. &c.—and a great deal to that purpose:—Well, you may take my word that nine parts in ten of a man's sense or his nonsense, his successes and miscarriages in this world depend upon their motions and activity, and the different tracks and trains you put them into (1.1.1)
Tristram begins the novel by asserting that identity is fixed before birth, and that it passes directly from father to son (no word on the X chromosome). There's no room for individuality in this notion of identity. Identity depends entirely on where you come from, not where you're going.
| Quote #2
In writing what I have set about, I shall confine myself neither to his rules, nor to any man's rules that ever lived. (1.4.3)
Tristram seems to find a sense of identity in his writing—and a radical one, too, where he's a lone wolf, completely adrift from society and family. But how serious is he? At other points, he complains about how difficult it is to avoid plagiarism, and lots of his writing responds to or even directly copies other writers. Like Tristram the character, Tristram the writer has a hard time telling us exactly who he is.
| Quote #3
It is a history-book … of what passes in a man's own mind. (2.2.7)
If the novel is a history of what passes in a man's mind, then the novel as a whole is a key to Tristram's identity—not just what he says about himself, but what he says about everyone else and, importantly, the way that he says it. If Tristram were writing today, he'd definitely have a Tumblr.