The Fishbone Diagram (also called the Ishikawa Diagram or Cause-and-Effect Diagram) is a visual tool for mapping all potential causes of a problem, organised by category. Developed by Kaoru Ishikawa at Kawasaki shipyards in the 1960s, it provides a structured approach to brainstorming multiple causal hypotheses before committing to investigation — preventing the common error of fixating on the first plausible cause found.
Gresham's Law — 'bad money drives out good' — is an economic principle stating that when two forms of currency are legally considered equivalent, the one with lower intrinsic value tends to drive the higher-value one out of circulation. People hoard the good money and spend the bad. The principle generalizes broadly: in any environment where good and bad versions of something are treated as interchangeable, the bad tends to crowd out the good.
Root Cause Analysis (RCA) is a systematic process for identifying the fundamental causes of problems — not just their symptoms — so that interventions prevent recurrence rather than merely resolving the immediate incident. Developed in industrial safety and quality management, RCA has become standard practice in healthcare, software engineering, aviation, and organisational management for post-incident learning.