From "intentionally" to Intensionality: the formal semantics of mental state adverbs in English and German law

The year is 2024, and Charles is the King of the United Kingdom. Paul, an anti-royalist, has not heard that the Queen died and thinks Charles is still the Prince of Wales. He kills Charles.

Is Paul guilty of regicide? The sentence "Paul intentionally killed Charles" is true. However, "Paul intentionally killed the King" is ambiguous, although Charles and the King are the same person.

The statement is false on account of how it says what it says (it is false de dicto). How could Paul intentionally kill the King if he didn't know that the person he was killing was the King? On the other hand, there is a person who is the King and it is true that Paul intentionally killed this person.

It is indeed true of the actual person he killed that Paul killed them intentionally (it is true de re). Therefore, "Paul intentionally killed the King" is true. That sentences can be ambiguous is well-known.

But how can the law be applied fairly if the language used to convey it is potentially ambiguous between de re and de dicto readings?

In order to ensure fairness in the courtroom, it is necessary to understand how mental state adverbs (e.g., "intentionally", "accidentally") and the de re/de dicto ambiguity are dealt with in the law. Rodes (1998) and Anderson (2014) investigate the role of the de re/de dicto ambiguity in the law based on mental state verbs (e.g., "believe", "intend").

Anderson suggests that lawyers are de re biased and neglect de dicto readings because they are more abstract in that they do not involve an entity in the real world. Bix (2014) criticizes the underlying data in Anderson (2014), as her court cases are from different countries and centuries. I want to fill this gap by using legal databases from England and Germany for a specific time frame and compare how the de re/de digto ambiguity is dealt with in common (UK) and civil (GER) law.

This comparison is interesting as it has been claimed that lawyers in these two legal systems think differently (e.g. Legrand 1996; La Porta, Lopez-de-Silanes, & Shleifer 2008). Furthermore, this will allow me to enrich the intersection of linguistics and law which has been focused on the US until now.

Rodes (1998) and Anderson (2014) only considered cases involving mental state verbs. These verbs and their behavior wrt. the de re/de dicto ambiguity have been thoroughly researched (see e.g., Hintikka 1969, Hirsch 2018, Pearson 2020, Kamath and Bradford 2023, Keshet and Schwarz 2019, Nelson 2019). However, mental state verbs and adverbs behave differently.

Consider again the case above. "Paul believes that he killed the King", like the sentence with "intentionally", is false de dicto, but true de re. By contrast, consider a case in which Paul killed Charles under the false belief that he was the King and the Queen had died. "Paul believes that he killed the King" is now true de dicto (in his mind, he killed the King) and false de re (the person he killed is not the King).

On the other hand, "Paul intentionally killed the King" is false de re (the person he killed is not the King) AND de dicto (in his mind, he killed the King, but this is not enough, as it still seems false that he killed the King intentionally if he did not actually kill the King) as well. Mental state adverbs have not received much attention beyond Thomason and Stalnaker (1973) and Bonami et al. (2004) although they clearly behave differently to verbs.

Since the difference between mental state verbs and adverbs could influence whether a person is deemed to have acted with intention, it is vital to expand on Anderson's (2014) work by exploring mental state adverbs and the law. A precise formal semantic analysis of these adverbs is necessary to determine in which contexts the de re/de dicto ambiguity arises, in order to ensure that the law can be applied fairly.

Finally, this project will serve as the basis for evidenced-based guidelines for lawyers, judges and juries on how to recognize de re/de dicto ambiguities.