If you read the paragraph that referenced it, it appears he's referring to constructs like 'if' statements and 'while' loops. In particular, he was contrasting the difference between mechanical engineering and software engineering:

> If I wanted to put an ‘If’ statement in a ‘While’ statement, I don't have to worry about whether the ‘If’ statement will oscillate at a certain frequency and rub against the ‘While’ statement and eventually they will fracture. I don't have to worry whether it will oscillate at a certain higher frequency and induce a signal in the value of some other variable. [...]