"Oromis - What is the most important mental tool a person can possess? Eragon - Detrrmination. Oromis - [...] no. I meant the tool most necessary to choose the best course of action in any given situation. Determination is as common among men who are dull and foolish as it is among those who are brilliant intellects [...] Eragon - Wisdom, wisdom is the most important for a person to possess. Oromis- A fair guess, but, again, no. the answer is logic. Or, to put it another way, the ability to reason analytically.Applied properly it can overcome any lack of wisdom, which one only gains through age and experience.