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The article discusses the use of "natural" or external keys (such as chassis numbers, Social Security Numbers, etc.) in database design. The author argues that it's generally not a good idea to use these types of keys because they can be prone to errors and changes over time. He shares his personal experience with a car's chassis number being incorrect, which highlights the potential problems with using natural keys.The article also explores some common issues with using natural keys, including:* Uniqueness: A natural key may not always uniquely identify an entity.* Data-entry errors: Clerical errors can occur when entering or updating external data.* Changes over time: External data can change, making the natural key no longer valid.The author concludes that synthetic keys are generally a better choice for database design, as they allow for greater control and flexibility in managing data.