Defeasible Logic
There are two levels of proof available.
(1) The definite level. 

This level only uses facts and rules with > in them.
To prove x at this level, type
+D x
(2) The defeasible level. 

This level uses all the facts, rules and the priority (> ) information.
To prove x at this level type
+d x
This system can also prove that formulas cannot be proved.
To prove that +D x cannot be proved, type
D x
To prove that +d x cannot be proved, type
d x
The positive (+ ) and negative ( ) kinds of
proof are related as follows.
Let P be D or d .
If +P x then not P x .
If P x then not +P x .
The levels of proof are related as follows.
If +D x then +d x .
If d x then D x .
Defeasible Logic Variants
The dt level of proof does not feature team defeat, but
is otherwise the same as the d defeasible level of proof.
The da level of proof features ambiguity propogation,
making it a slightly stronger level of proof than the d
defeasible level of proof. It is defined in terms of a weaker level,
S , support.
