What does it mean that redundant relationships provide resilience?

Multiple paths between important nodes make a system more robust.

Example: The Space Shuttle's flight computer system used five General-Purpose Computers, four running identical software in lock-step synchronization and one backup running independently written code. At the end of every clock cycle, the four primary computers voted on the correct output. If one computer failed, the remaining three continued voting. If two failed, the remaining two could still cross-check. If three failed, the independently programmed fifth computer took over. NASA designed the system to a 'Fail Operational, Fail Operational, Fail Safe' criterion — meaning it had to remain fully operational after any single failure, fully operational after any second failure, and still land safely after most kinds of third failure. The redundant relationships between computers meant that no single hardware failure — or even two — could kill the crew. The system didn't just tolerate failure. It expected it.

Try this: Map one critical dependency in your life — a skill, a relationship, a tool, an income source, or an information channel that, if it disappeared tomorrow, would cause serious disruption. Now identify your current redundancy level for that dependency. Do you have zero backup paths (single point of failure), one alternative (basic redundancy), or two or more alternatives (robust redundancy)? For anything at zero, design one concrete backup path you could establish this week. For anything at one, ask whether your backup is truly independent — or whether it shares a failure mode with your primary path. Write down the dependency, its current redundancy level, and your proposed improvement.