Argdown FAQ

What is the difference in Argdown between - and ><?

Example:

[Vegetarianism]
  - [Omnivorism]

[Omnivorism]
  - [Vegetarianism]

is the same as?

[Vegetarianism]
  >< [Omnivorism]

The short answer

The short answer is: - is used for defining a contrary statement relation, >< is used for defining a contradictory statement relation. If you don't know the difference, you are probably just fine if you only use - and forget about ><. The latter is only handy in special cases and only for logical experts.

The longer answer is a little bit more complicated.

Using -

- can be used between:

1. two statements [E1] - [E2] (in this FAQ I am leaving out the line break and indentation for simplicity's sake)
2. two arguments (with or without reconstruction) <E1> - <E2>
3. an argument and a statement (with or without reconstruction) [E2] - <E1>

ad 1.) In the first case [E1] - [E2] is interpreted as defining a contrary relation between two statements A and B which means: If [E2] is true, then [E1] is false. Those schooled in logic will know that this does not also mean that if [E2] is false, [E1] will be true. The difference between a contrary and contradictory relation is precisely that this second relation is only implied by the latter, not the former.

From the logical relation between sentences expressed in [E1] - [E2], dialectical attack relations are derived, if E2 is a conclusion of an argument.

ad 2.) In case 2.<E1> - <E2> will simply be interpreted as an "informal" attack relations that has not been logically reconstructed yet. We can not say which premise in <E1> is attacked by <E2>, we simply state, that some premise is.

ad 3.) In case 3. how [E1] - <E2> will be interpreted depends on the state of . If it is not reconstructed, it will once again be simply interpreted as an informal dialectical attack relation. If <E2> has been reconstructed, [E1] - <E2> is interpreted as expressing a contrary relation between <E2>'s conclusion and [E1] and thus also as a logically reconstructed dialectical attack relation of <E2>.

Using ><

>< can only be used between two statements or a reconstructed argument and a statement. In both cases a contradictory relation between two statements is expressed. Depending on if one of those statements is used as a conclusion in an argument, logically reconstructed attack relations may be inferred from this logical relations.

• [E1] >< [E2] means: If [E1] is true, [E2] is false. And if [E1] is false, [E2] is true.

• <E1> >< [E2] or [E2] >< <E1> means: If <E1>'s conclusion is true, [E2] is false. And if <E1>'s conclusion is false, [E2] is true. Because one of the statements is used as a conclusion in the argument <E1>, this defines also a logically reconstructed attack relation of .

What is the default direction of - and +?

• - is only a short form of <-
• + is only a short form of <+

In all these cases the statement or argument of the current line is the source of the relation, while the parent statement or argument is the target. Thus, these relations define 'outgoing' relations for the element in the current line, while -> and +> define 'incoming' relations of the element in the current line.