There are two meaning of the term “argument” – in the broad sense and in the narrow legal sense. In the first case, it is proof as the establishment of truth, the correspondence between the statement and reality. In the second case. it is evidence that serves to convince a judge and jurors that statements are true. At the same time, argument in the narrow sense can be considered from three sides: a) as a means of persuasion, b) as the basis of persuasion, and c) as a process of proving. Since forensic evidence must meet not only legal, but also logical requirements, this article examines the use of rules of inference by lawyers. Leaving induction, analogy and abduction out of the current study, the authors focus on deduction in legal works. The subtleties of the use of deductive reasoning in the process of proving are considered. The analysis involved the reasoning of lawyers used to defend the accused in the trial, both famous and modern, as well as the construction of reasoning by fiction characters. It is shown that the correct construction of deductive reasoning ensures the effectiveness of argumentation. The examples show the complex use of deductive reasoning in legal argumentation. Lawyers consistently apply syllogisms, smoothly moving from one type to another, combining a categorical syllogism or a purely conditional syllogism with a conditionally categorical or divisive-categorical syllogism. The process of proof does not consist of a single deductive conclusion, but connects various syllogisms into a consistent chain, ensuring the effectiveness of judicial argumentation.
Harmash et al. (Tue,) studied this question.