To catch a thief with and without numbers: arguments, scenarios and probabilities in evidential reasoning

Abstract

Mistakes in evidential reasoning can have severe consequences. Especially, errors in the use of statistics have led to serious miscarriages of justice. Fact-finders and forensic experts make errors in reasoning and fail to communicate effectively. As tools to prevent mistakes, three kinds of methods are available. Argumentative methods analyse the arguments and counterarguments that are presented in court. Narrative methods consider the construction and comparison of scenarios of what may have happened. Probabilistic methods show the connections between the probability of hypothetical events and the evidence. Each of the kinds of methods has provided useful normative maxims for good evidential reasoning. Argumentative and narrative methods are especially helpful for the analysis of qualitative information, but do not come with a formal theory that is as well-established as probability theory. In probabilistic methods, the emphasis is on numeric information, so much so that a standard criticism is that these methods require more numbers than are available. This article offers an integrating perspective on evidential reasoning, combining the strengths of each of the kinds of methods: the adversarial setting of arguments pro and con, the globally coherent perspective provided by scenarios, and the gradual uncertainty of probabilities. In the integrating perspective, arguments and scenarios are interpreted in the quantitative setting of standard probability theory. In this way, the integrated perspective provides a normative framework that bridges the communicative gap between fact-finders and forensic experts. Both qualitative and quantitative information can be used safely, focusing on what is relevant.

Formalizing value-guided argumentation for ethical systems design

“…Our approach is not based on abstract argumentation, but has been developed in a way to stay close to classical logic and standard probability theory (see Verheij 2012Verheij , 2014Verheij , 2016b. Bench-Capon modeled the promotion and demotion of values as an argument selection mechanism.…”

“…The following formal perspective has been developed in recent research on evidential argumentation, in order to bridge between qualitative or quantitative modeling primitives, in particular arguments, scenarios and probabilities (Verheij 2014(Verheij , 2016cVerheij et al 2016), building on (Verheij 2010(Verheij , 2012. In subsequent sections, we show how the formalism also can be put to work for ethical decision making and its context-dependence, value-dependence and rule-dependence.…”

“…In recent research on evidential argumentation (Verheij 2014), a model has been developed for the connection between qualitative and quantitative modeling primitives. That model was designed as an answer to lessons learnt in research on the modeling of arguments and scenarios for evidential reasoning in Bayesian networks .…”

“…In this paper, the model presented by Verheij (2014) is applied to the comparison of values in ethical decision making, emphasising the role of context-dependence, value-dependence and rule-dependence. In this way, we provide a perspective on ethical decision making as value-guided argumentation.…”

Proof with and without probabilities

“…Building on ideas presented semiformally by Verheij (2014b), in the present paper, a formalism is proposed in which presumptive arguments about coherent hypotheses can be compared in terms of their strengths. The formalism allows for a qualitative and a quantitative interpretation.…”