•Why it earns a slot
Why it earns a slot: this is the single essay that explains why the U.S. government is built to move slowly and fight itself on purpose. Every modern complaint about gridlock is, in some sense, an argument with Madison's design choice.
Madison's answer to why a constitution needs checks and balances at all: because you cannot trust good motives to survive contact with power.
This distillation is written from the freely available original, which is always the better read when you have the time: Project Gutenberg.