I frequently ride out and take the air;—though sometimes, to my shame be it spoken, I take somewhat longer journeys than what a wise man would think altogether right.—But the truth is,—I am not a wise man;—and besides am a mortal of so little consequence in the world, it is not much matter what I do; so I seldom fret or fume at all about it:
Tristram is in on the joke. He admits here that he has his own hobby-horse and that he doesn't always act wisely when pursuing it. This is a good articulation of Shandyism: "it is not much matter what I do; so I seldome fret or fume at all about it." We can get down with that philosophy.
He chose rather to join in the laugh against himself (1.10.8)
Tristram describes Yorick's attitude towards his own folly, which is shockingly similar to Tristram's and, we bet, Sterne's—he laughs at it. This seems to be the right approach throughout the novel, and probably for life: better to laugh with than be laughed at.
"would be the most grave or serious of mortal men for days and weeks together;—but he was an enemy to the affectation of it, and declared open war against it, only as it appeared a cloak for ignorance, or for folly" (1.11.6)
Yorick hates seriousness not for itself but because people use it to hide their foolishness (folly). He wants everyone to celebrate folly and enjoy being foolish—basically, the class clown of the novel.
Nothing in the whole affair provoked him so much as the condolences of his friends, and the foolish figure they
should make at church the first Sunday (1.16.3)
Mr. Shandy's major preoccupation on the journey back to Shandy Hall from London after Mrs. Shandy's fake pregnancy isn't his wife's health but the fact that people are going to think he's foolish. Of course, being afraid of looking dumb just makes you act dumber. Just think, if Mr. Shandy hadn't wanted to get back at his wife by making her give birth in the country, Tristram's nose would never have been broken.
I would sooner undertake to explain the hardest problem in Geometry than pretend to account for it, that a gentleman of my father's great good sense,—knowing, as the reader must have observed him, and curious too in philosophy,—wise also in political reasoning,—and in polemical (as he will find) no way ignorant,—could be capable of entertaining a notion in his head, so out of the common track (1.19.1)
Good sense and learning won't keep a person from foolishness, so you might as well just embrace it—even someone as learned as Mr. Shandy can have crazy ideas. (Although—it does seem like Tristram is gently making fun of his father, here. Are we really supposed to believe that Tristram thinks his father has good sense? Doesn't seem likely.)
but as a warning to the learned reader against the indiscreet reception of such guests who, after a free and undisturbed entrance, for some years, into our brains,—at length claim a kind of settlement there,—working sometimes like yeast;—but more generally after the manner of the gentle passion, beginning in jest,—but ending in downright earnest.
Here's a little warning that foolishness can sneak up on a person. Over the years, jokes can gradually turn someone into a full-fledged nut; one cat can turn into 550; and the story of your life can turn into a nine-volume masterpiece of digression.
So much for my chapter upon chapters, which I hold to be the best chapter in my whole work; and take my word, whoever reads it is full as well employed, as in picking straws.
Even the reader can't escape being a fool. By reading his chapter, Tristram says, you, the reader, have been "picking straws," engaged in a useless task. Gotcha: the very act of reading Tristram Shandy is a folly.
He shall neither strike, or pinch, or tickle—or bite, or cut his nails, or hawk, or spit, or snift, or drum with his feet or fingers in company;—nor (according to Erasmus) shall he speak to any one in making water,—nor shall he point to carrion or excrement.—Now this is all nonsense again, quoth my uncle Toby to himself.— (6.5.6)
Mr. Shandy is a fool because he combines ideas from too many people. He is so wrapped up in his reading that he completely loses common sense when he's trying to decide what kind of tutor he wants for Tristram. The result? A mishmash of qualities that can't possibly exist in one person.
And the five following, a good quantity of heterogeneous matter be inserted, to keep up that just balance betwixt wisdom and folly, without which a book would not hold together a single year: (9.12.1)
If Tristram Shandy were all wise and serious, it would be an extremely dull book. Tristram here announces that he's carefully mixed wisdom with folly in order to produce a book that's fun to read but can also teach you something about life, like a little chocolate powder mixed in with your protein shake. Foolishness has its place in the world, just like wisdom.
A COCK and a BULL, said Yorick—And one of the best of its kind, I ever heard.
In the last line of the book, it seems like Tristram (or Yorick, really) is dismissing the entire thing as a joke. Is he being serious? Well, how much do you trust Tristram as an author? Does he know what he's doing, or is the whole book just one big Shandyean hobby-horse?