“arg2012 ” — 2012/10/13 — 22:51 — page 41 — #41 The Dialogical Force of Implicit Premises. Presumptions in Legal

Abstract. In the logical and rhetorical tradition, enthymemes have often been described according to two criteria: their structure and the epistemic status of their premises. These two characteristics are strictly connected to each other, since the major premise of an enthymeme can be taken for granted because it is commonly considered as likely. However, what is the relationship between likeliness and the possibility of taking a proposition for granted? Why does a speaker decide to leave a premise unexpressed? These two questions can be addressed by considering the pragmatic and the rhetorical perspectives. The purpose of this work is to investigate legal enthymemes, inquiring into their peculiar defeasible nature which makes them context-relevant and audience oriented. We maintain that the act of hiding a proposition needed to make the inference correct transforms the syllogistic type of reasoning into a powerful rhetorical strategy for both the speaker and the hearer. We claim that enthymemes can be considered as instruments of persuasion grounded on presumptions. The choice of an implicit premise becomes, in this perspective, a strategy of selecting what a specific interlocutor can hold as more likely based on his knowledge or values. For this reason the notion of kairos, the opportunity and contextual effectiveness of a premise, becomes crucial. An implicit premise should be regarded not only as an element that the speaker takes for granted, but as a strategic instrument for shifting and increasing the burden of proof. aInstituto de Filosofia da Linguagem – FCSH-UNL, Lisboa, Portugal