PithyMaxims

Write smaller things.

—Sandi Metz

Write programs that do one thing and do it well.
Write programs to work together.
Write programs to handle text streams, because that is a universal interface.

—Doug McIlroy

Write more datastructures.

—Richard Feldman

Write more state machines.

—me

What's the intersection of all of these? They certainly don't seem to me to describe incompatible visions of programming. Rather, they all seem to be pointing toward the same thing.

Know when you're dealing with data and data transformation, when you're dealing with a state machine, and when you need to perform side effects. Don't make something an object (i.e. a state machine) when it can just be data. Only perform side effects if you absolutely must. Write small, abstract pieces that compose. Let objects communicate via ubiquitous interfaces. Keep hierarchies shallow.