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D.Luzeaux [6] shows how to translate a n-opposition structure into **an epistemistic logic. We had found**
modalitites of a defeasible logic introduced in [1] organized in a n-opposition structure according to their definitions. This structure looks like the one we designed for the experiment. Defeasible reasonings deals with conflictual statements. Defeasible logics were introduced by D.Nute [8].

A defeasible theory is a triple (F,R,>) where F is a set of facts, R a set of rules and > **a superiority**
relation. There are three kinds of rules, strict rules, defeasible rules and defeaters.

1. Facts are a set of literals and represent indisputable knowledge .

2. Strict rules are denoted by A− > B **and are interpreted in the classical sense.**
3. Defeasible rules are rules that can be defeated by contrary evidences.

4. Defeaters are rules that cannot be used to draw any conclusions. Their only use is to prevent conclusions.

In other words, they are used to defeat some defeasible rule by producing evidence to the contrary.

5. A superiority relation on R is an acyclic relation > **on R.** r1 > r**2 expresses that r1 may override r2 if**
they lead to conclusive decision that contradict each other.
A conclusion in a defeasible theory D is a tagged litteral with one of the **following modality:**
1. +∆q **means that q is definitely provable in D. q is proved with only facts and strict rules.**

2. −∆q **means that q is not definetly provable in D. q is not proved with only facts and strict rules.**
3. +δq **means that q is defeasibly provable in D. A defeater to contradict q can exist. The superiority**
relation leads to conclude q before ¬q.

4. −δq **means that q is not defeasibly provable in D. No set of rules lead to conclude q or for every set of**
rules leading to conclude q, the superiority relation leads to conclude ¬q **before.**
5. +δapq **means q is provable with ambiguity in D. There is a set of rules that can lead to conclude q.**
The superiority relation is not taken into account.

6. −δapq means that q is not provable even with ambiguity in D. There is no set of **rules that can lead to**
conclude q.