True lies

Max Urchs (Szczecin University)

There are many types of deceptive speech acts. Lies are one of them: they have an internal structure, they serve rational aims. So it seems only natural to ask for an analysis of the formal structure of lies. Obviously, there is a role to play for logic, too.

In his 1990 analysis of lying Jerzy Pelc ([2]) mentions several "dimensions of truth" necessary for a complete representations of that phenomenon.Taking this for granted, lying shall be a thorny field for logical investigation.

Logic is (devoted to and) making use of logical calculi, i.e. consequence operations in some formal language. The characteristic point is: there is no extra-language reasoning. It would be naïve to hope for a complete and exhaustive analysis of lying by means of logic alone. Still one might expect that logic comes up with a framework that grasps the essential features of lying - after all, modern logic is more flexible and much more powerful than it was twenty years ago. Recent work in cognitive science, and especially in A.I., drives logic towards non-monotonic, causal or inconsistency-tolerant forms of inference.

I will mention some of these formal approaches ([1], [4]), concentrating my own analysis on cases of lying while saying something which is literally true. The interesting examples of such speech acts do mislead the hearer by faky assurance, i.e. the deception is hidden in the performative aspect of the utterance. Resulting problems seem close to Cohen's paradox (cf [3]) .


Jörg Meibauer, "Lying and falsely implicating", Journal of Pragmatics 37, 2005, 1373-1399.

Jerzy Pelc, "O pojęciu kłamstwa - z punktu widzenia semiotyki", Studia semiotyczne 1990, 289-297.

William G. Lycan, Philosophy of Language. A contemporary introduction , Routledge, London, 2000.

Hans Rott, "Der Wert der Wahrheit", in: Kulturen der Lüge (Mayer, ed.), Böhlau, Weimar, 2003, 7-34.