Logical Studies For Minimal Agency

Agency is usually used to denote the manifestation of the capacity to perform intentional actions,so it is clear that agency is the internal mechanism of intentional action.Since the aim of philosophy of action is to explain the agency embodied in action,agency in different theories of action may have different metaphysical burdens.The current logics of agency have characterized the important feature of agency in many aspects and they have a close relationship with philosophy of agency.Both the philosophical and the logical research on agency will contribute to the understanding of the human-to-world relationship and to the study of artificial intelligence.This dissertation starts with clarifying the meaning of action and agency as well as the relationship between them and then it illustrates the fundamental role of minimal agency in intentional action.Based on this,a logical investigation in terms of minimal agency is established.The purpose of the clarification and the logical investigation is to demonstrate the real link between the philosophy of and the logic of agency,along with the possible link lies between the philosophy of agency and the logic of minimal agency.To be more specific,this dissertation has completed the following work:Firstly,it demonstrates the close relations between action and agency,and furthermore a new outline of action hierarchy theory is proposed based on Methodology of Logical Actionism.At present,there are mainly three theories of action that have defined and explained the notion of action,i.e.,the causal theory of action,agent causalist theory,and new volitionalism.However,all of them have encountered difficulties in explaining agency.In this dissertation,it is contended that those difficulties are inevitable because of the usage of agency in an unstratified sense.Based on the Methodology of Logical Actionism and Lynne R.Baker's hierarchical theory of agency,the stratification theory of action is given in accordance with the hierarchical agency,which puts agency at the core of action while retains agent's important position in intentional action.Secondly,it summarizes several representative logics of agency and discusses their relation with philosophy of agency.There are mainly three methods available to depict agency from a semantic view,namely,the dynamic semantics,the branching time semantics,and the neighborhood semantics.The dynamic semantics has its merit in describing "agents who are embarking on particular courses of action",and thereby it is possible to use this semantics to combine the mental state of an agent and the process of acting.The advantage of the branching time semantics is that it can combine agent's choice process with the possible historical states of the world,so it can express precisely the connection between agent and sates of affairs.The neighborhood semantics is more powerful in formalizing the agency in a macro scale,and we could avoid most logical omniscience problems by applying it to characterize "agency with mental states".Thirdly,it analyses the relationship between apt action and minimal agency and investigates the logical properties of the core elements of apt action separately with the neighborhood semantics and the relational semantics based on non-normal worlds.The basic elements of apt action are "intention","can",and "bring it about",the formal relation of which can be better described by virtue of the neighborhood semantics.However,the neighborhood semantics is not intuitive when used in interpretation and though it is more complex,the relational semantics based on non-normal worlds is more straightforward in interpretation than the neighborhood semantics.In fact,the two semantics are equivalent.It needs to be noted that this description exactly portrays two specific cases of intentional action:accidentally successful action and failed action.This work lays foundations for analysing intentional action in a formal way.Therefore it is helpful to demonstrate the logical structure of practical reasoning.Fourthly,the branching time semantics is given to characterize "intentional trying".Intentional causation is a very important notion for explaining agency.If we regard "attempt",which represents the intentional causation,as a kind of mental state like what Jennifer Hornsby has put it to be,then various problems will emerge.In order to avoid this defect,"intentional trying" is defined as an intentional action.By this definition,it is not only possible to analyse intentional action more precisely,but is also possible to give an exposition for the relationship between branching time,agent's choice and contingency.As a consequence,we are able to explain the function of intentional causation in minimal agency.Finally,the dynamic semantics is provided to describe two basic types of action.Generally,the procedural aspect of agency can be expressed through action variables,so we can enrich the expression of agency by inserting action variables into the intentional causation.Whether it is the action by commission or by omission,it cannot be separated from minimal agency.Based on the dynamic semantics,the two actions are described semantically.This result is used as a formal method to analyse the procedural minimal agency in terms of action types.Through the work above,three basic conclusions are obtained:1.Different semantics have their own strength and weakness in characterizing action or agency,so it is necessary to combine them to some extent;2.Characterizing "minimal agency"is the basic work for analysing intentional action and higher-order agency;3.Characterization and analysis on "minimal agency" can promote the interaction between philosophy of agency and logic of agency and this research area may probably leave a great room for theoretical development in the future.