Legal Definitions - a fortiori

A fortiori, Latin for "from the stronger," describes an argument that holds true with even greater force because a related, weaker premise has already been established. It signifies that if something is true in one instance, it must be "even more so" true in a more compelling or stronger instance.

The Latin phrase a fortiori (pronounced "ah for-tee-OR-ee") is used in legal arguments to indicate that if a certain conclusion is true under one set of circumstances, it must be true with even greater certainty or stronger logical force under a different, more compelling set of circumstances. It essentially means "with even stronger reason" or "even more so."

When an argument uses a fortiori, it suggests that a conclusion drawn from a less obvious or less extreme situation applies with undeniable force to a more obvious or more extreme situation, based on the same underlying principle.

• Example 1: Public Safety Regulations
  If a city ordinance prohibits parking a commercial truck on a residential street overnight due to noise and space concerns, then a fortiori, it prohibits parking a large, unattended construction crane there.

  Explanation: The underlying principle is to prevent large, potentially disruptive or hazardous vehicles from occupying residential streets. If a commercial truck is deemed problematic, a construction crane, being significantly larger, heavier, and potentially more dangerous, falls under the same prohibition with even stronger logical justification.

• Example 2: Contractual Obligations
  If a contract specifies that a builder must use high-quality, brand-new materials for a home renovation, then a fortiori, they cannot use salvaged or damaged materials.

  Explanation: The contract establishes a standard for material quality. If the builder is obligated to use new, high-quality materials, then using materials that are demonstrably inferior (salvaged or damaged) would be a violation by an even greater measure, as it directly contradicts the established standard.

• Example 3: Professional Conduct
  If a company's code of conduct requires employees to treat all clients with respect and professionalism, then a fortiori, it prohibits employees from making derogatory remarks about clients on social media.

  Explanation: The core principle is respectful and professional client interaction. While direct disrespect in person is a violation, making derogatory remarks publicly on social media amplifies the harm to the client and the company's reputation, thus violating the code of conduct with even stronger justification.