What does it mean that causal chains are sequences of relationships?

Tracing a chain of causes and effects reveals the full mechanism behind an outcome.

Example: In September 1854, physician John Snow traced a cholera outbreak in London's Soho district by mapping deaths and walking the causal chain backward. He started with an observation: deaths clustered around the Broad Street water pump. Working with Reverend Henry Whitehead, Snow traced the chain link by link — from cholera deaths, to contaminated water consumption, to the Broad Street pump, to a leaking cesspool beneath a nearby house, to the soiled diapers of an infant with cholera who lived at 40 Broad Street. Each link was a relationship: the cesspool contaminated the well, the well fed the pump, the pump served the neighborhood, the neighborhood drank the water, the water carried the pathogen. Remove any single link and the chain breaks. Snow didn't just identify the cause — he traced the entire mechanism. That is what a causal chain does: it converts a mysterious outcome into a sequence of individually verifiable relationships.

Try this: Pick a significant outcome in your life from the past six months — a project that succeeded, a habit that collapsed, a relationship that shifted. Now trace the causal chain backward using exactly five links. Start with the outcome and ask 'What directly caused this?' for each link. Write each link as a relationship statement: 'A caused B because [mechanism].' Then examine your chain for gaps: is there a link where you wrote 'caused' but cannot explain the mechanism? That gap is where your understanding is weakest. Finally, test one link by asking: if I removed this link, would the outcome still have occurred? If yes, your chain has a spurious link that needs replacing.