Listen up, Shmoopers, because Tristram has something to say. Actually, he should have said it a long time ago, but it's going to fit better here.
Remember: Mr. Shandy is the guy with lots of odd opinions. He doesn't like to listen to others and prefers to come to his own conclusions about everything.
Because of that, he tries out a weird argument to try to convince Mrs. Shandy to accept Dr. Slop instead of the midwife. The argument rests on two axioms: (1) A man's own wit (cleverness) is better than another man's; (2) Wit has to come from every man's own soul.
Obviously, souls are all equal. Difference in wit, however, come from the way the body is organized in the place where the soul lives.
Since people can walk around and be brain dead, it's obvious that the soul doesn't live there, as the philosopher Descartes says. And something so noble as the soul couldn't possibly live in the pool of liquid in the brain, as another authority says. So it must live somewhere around the medulla oblongata.
Okay, so Tristram is buying what Mr. Shandy is selling so far. But here, Mr. Shandy goes off on his own Shandean hypothesis. Mr. Shandy's main concern is to produce the best heirs possible.
To do this requires (1) being careful during the heir's conception, i.e., s-e-x; (2) giving the child the best name possible; and, (3) preserving the delicate head during birth.
Let's break it down.
Mr. Shandy is horrified to know that, because a child's head is so soft, it gets malformed and crushed in labor. He figures that this is responsible for people's inability to think straight—labor propels the cerebrum (brain) toward the cerebellum (seat of the understanding). Let us remind you that you should not use Tristram Shandy as a replacement for a good anatomy textbook.
In fact, this explains why the eldest son is usually the dunce of the family: he opens the way, literally, for his younger brothers. It also, in a sublimely racist moment, explains why Asians are smarter: nature had laid a lighter tax upon the fairest parts of the creation (2.19.28).
If, however, a doctor extracts the child feet first, the cerebellum is propelled toward the cerebrum, and all is well. Even better is the C-section, which is responsible for the births of so many geniuses.
Mrs. Shandy, however, is not too thrilled with the suggestion of a C-section—which, if you ask us, considering the dearth of antibiotics and lack of basic understanding of sterilization, seems like a reasonable response.
So Mr. Shandy resolves to try the second best way: getting the doctor to extract the child feet first. Dr. Slop doesn't care too much about the soul, but he firmly believes in extraction as the latest obstetrical triumph.
Let the reader imagine how poor modest Uncle Toby feels about the ensuing discussion of labor and birth—and, while you're at it, imagine how Tristram lost his nose and gained his ill-fated name. It's a regular soap opera in the Shandy household.