YAMADA Tomoyuki

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YAMADA Tomoyuki Professor

Philosophy and Cultural Sciences / Philosophy
Specialized Field
Philosophy of Language, Mind, and Action
Research Subject
I have been working on Philosophy of Language, Mind, and Action, especially Speech Acts and the Mind-Body Problem, mainly drawing on works in the analytic tradition broadly construed.
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Lab. Letters: Messages from the Laboratory

What do people accomplish with words?
ーDynamic Modal Logic of Speech Actsー

The Gap

When we think of rational agents involved in social interactions, the distinction between illocutionary acts and perlocutionary acts introduced in Austin (1955) seems to be of vital importance to a clear understanding of what such agents accomplish by their speech acts. For instance, van Benthem and Liu consider a command ``see to it that φ!'' as a trigger of preference change, and say that ``intuitively,'' it ``makes worlds where φholds preferred over those where it does not -- at least, if we accept the preference induced by the issuer of the command,'' (van Benthem and Liu, 2007). The need they felt for the proviso here reflects an important logical gap between what an illocutionary act of commanding involves and perlocutionary effects it may have upon our preferences. Rational agents are not controlled mechanically by speech acts in the way in which voice controlled machines are controlled. It is possible for us to disobey a command even if it is effective.

Dynamified Logics of Speech Acts

Inspired by the development of various systems of DEL (Dynamic Epistemic Logic), I developed a few versions of DMDL (Dynamified Multi-agent Deontic Logic) and other dynamified modal logics in order to capture the effects illocutionary acts such as commanding, promising, requesting, asserting, and so on have by virtue of their being of such kinds of acts. The following diagram shows the two models of the simplest version of DMDL (called ECL) which represent the situations before and after your boss’s act of commanding respectively.

  • Your boss’s command !ap change the model M into M!ap .


If you are interested in how language works in situations and changes them, you are invited to join us and study speech acts with us.


Philosophers love paradoxes. 5th Humanity Café, May 2011, Kinokuniya

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