1 Dichotomies and Oppositions in Legal Argumentation FABRIZIO MACAGNO

In this paper we use a series of examples to show how oppositions and dichotomies are fundamental in legal argumentation, and vitally important to be aware of, because of their twofold nature. On the one hand, they are argument structures underlying various kinds of rational argumentation commonly used in law as a means of getting to the truth in a conflict of opinion under critical discussion by two opposing sides before a trier of fact. On the other hand, they are argument structures underling moves made in strategic advocacy by both sides that function as platforms for different kinds of questionable argumentation tactics and moves that are in some instances tricky and deceptive. In this paper we analyze examples of legal argumentation based on reasoning from dichotomies and oppositions. We show how this type of argumentation is especially visible in cross-examination and voir dire. It is shown in the paper how reasoning from oppositions is a powerful argumentative instrument in law that can be used both to support an assertion and back a decision. Opposition and dichotomy are fundamental logical notions in logic, and in argumentation studies generally. In formal logic, there are two concepts of opposition. According to the strong sense of opposition expressed by classical negation, a pairs of propositions are contradictories if it is not possible for both to be true, and also not possible for both to be false. For example, the proposition ‘This pen is black’ and the proposition ‘This pen is not black’ are contradictories. The one proposition is true if and only if the other is false. According to the weak sense of ‘opposition’, one proposition can be the contrary of another if it is not possible for both to be true, even though it is possible that both are false. For example, the proposition ‘This pen is black’ (all over) and the proposition ‘This pen is green’ (all over) are contraries. In addition to this logical view of ‘conflict of opinions’, there is also a dialogical view (Walton, Reed and Macagno, 2008). Any critical discussion arises from an opposition of viewpoints between two parties to the discussion. A viewpoint contains a proposition, and an attitude, pro or contra. In the stronger kind of opposition, the one party has a pro attitude to a proposition and the other party has a contra attitude to that same proposition. In this strong kind of opposition, one party must refute the proposition held by the other party in order to win the dialog. In the weaker kind of opposition, the one party has a pro attitude to a proposition and the other party has neither a pro or contra attitude to that same proposition. He is simply unconvinced (sceptical about it being true). In the stronger kind of opposition, a party can refute the other and win merely by showing that her thesis is doubtful. In this paper, we argue that the logical notion of opposition is useful for helping us to understand how dichotomies and oppositions work in legal argumentation, in the end it is of limited usefulness because we need to see how oppositions and dichotomies can intervene at different levels in the frame of a legal discussion. To do this we analyze this kind of argumentation within the framework of a dialog procedure with three stages: an opening stage, an argumentation stage and a closing stage. To show how this pragmatic approach applies to legal argumentation in a nontechnical way that is still very useful, in section 3 we use the ancient stasis theory of Cicero. In this pragmatic model, reasoning is defined as a chaining together of inferences that can be used to try to settle some issue in a dialog that has two sides. A dialog is a sequence of moves in which two parties, a proponent and a respondent, take turns making moves – generally asking question, replying to question, and putting forward arguments. Such a dialog has a collective goal, and each participant has an individual goal. Rules determine which moves are legitimate as contributions to the dialog. Reasoning, as configured in this new pragmatic approach, is amenable to formalization