Legal Definitions - fidem mentiri

Fidem mentiri is a historical Latin term that literally translates to "to betray faith." It describes a situation where an individual breaks a solemn promise of loyalty, allegiance, or faithfulness, particularly within a structured or hierarchical relationship where such loyalty was formally pledged. Historically, it was used to describe a feudal tenant who failed to uphold the fealty (loyalty and service) sworn to their lord.

Here are some examples illustrating the concept of fidem mentiri:

• Imagine a medieval knight who had formally pledged his unwavering loyalty and military service to a duke. When a rival kingdom invades, the knight, instead of defending his duke's lands, secretly allies with the invaders and allows them passage through his own territory, directly aiding the enemy against his sworn lord.

  This exemplifies fidem mentiri because the knight has deliberately broken his solemn oath of fealty and loyalty to the duke, acting against the very person he was bound to serve and protect.

• Consider a high-ranking advisor to a monarch who has sworn an oath of absolute discretion and loyalty to the crown. Despite this oath, the advisor begins secretly leaking sensitive state secrets and strategic plans to a foreign power, intending to weaken the monarch's rule for personal gain.

  This situation illustrates fidem mentiri as the advisor has betrayed the profound trust and sworn allegiance to the monarch and the state, acting in direct opposition to their pledged duty.

• In a more modern, albeit analogous, context, think of a founding partner in a startup company who has signed a comprehensive partnership agreement outlining mutual trust, shared vision, and commitment to the company's success. This partner then secretly establishes a competing venture using the startup's proprietary information and actively poaches key employees and clients, all while still ostensibly working for the original company.

  While not a feudal oath, this scenario reflects the essence of fidem mentiri because the partner has fundamentally betrayed the foundational trust and loyalty inherent in the partnership agreement, acting against the collective interest they were sworn to uphold.