Studies In Prior's Tense Logic And Philosophy Thoughts

Authur Norman Prior(1914-1969)is a contemporary famous logician and philosopher in New Zealand.His academic research contains domains like tense logic,modal logic,hybrid logic,description logic,metaphysics,analytical philosophy and theology etc.,but his greatest achievement well-known by people is the creation of tense logic.In recent decades,his tense logic has been concerned frequently by people in foreign countries but the research literatures are few and not in-depth,and his philosophy thoughts related to it also lack introduction and research in our country.The research way of this thesis is as follows: based on overviewing tense logic relatively carefully,the thesis classifies and discusses Prior‘s tense logic and philosophy thoughts.Research emphasis is his work in the field of tense logic.The main line is his researches on tense involvement,determinism and indeterminism as well as time concept.It explores how he use tense logic to elaborate philosophy viewpoints like tense ontology and indeterminism,etc..Based on this consideration,it analyzes and evaluates his philosophy views including criticism to some of his ideas.The thesis consists of six parts.The part of preface firstly introduces the course of Prior‘s life and his main writings in the domain of tense logic and then summarizes the research status to his tense logic and philosophy thoughts.Finally,it points out the meaning of the research and the target.The first chapter sketches tense logic,on the basis of classifying the thought contexts and the foundation and the development of tense logic comparatively carefully,it mainly introduces the representative figures and views in each phase.The second chapter carefully introduces and analyzes Prior‘s tense logic and the relevant theory of four grades.Firstly,it sorts and shows multiple pure tense-logical systems and tense-modal logical systems presented by him and considers the semantics of some of those systems.Then,it carefully classifies the theory that ?four grades of tense-logical involvement‘ presented by him and introduces other scholars‘ discuss on his logic and philosophy.In my opinion,relatively speaking,concept definition is clear and the postulates adopted are fewest in the first grade system of the calculus of the earlier and later relation.The system is simplest.The second grade regards usually different kinds of formulas as the same level formulas.Compared with the first grade,it artificially complicates the first-order logic.The third grade introduced ?instant proposition‘,is a high-order logic.Its expressive power is strong,but too complicated.It is questionable as well that equating some instant with the conjunction of propositions which usually is true at this instant.It characterizes the privileged status of tense with the way of hybrid logic,but failed.As for the fourth grade,in addition to complexity,it also assumes time is ?unique‘.If not accepting the assumption,we can not translate the first-order logic of the earlier and later relation into the pure tense logic.The author concludes that the distinction from the first grade to the fourth is unreasonable and introducing the four grades of tense involvement is unnecessary.Furthermore,as regards researching tense logic,A-concepts are more fundamental than B-concets,but to be explained and illustrated by B-concepts in semantics.The third chapter systematically elaborates Prior‘s research to determinism and indeterminism with tense logic.It firstly introduces the argument that from the foreknowledge of God to the necessity of future.Wanting to insist on the creed of human freedom and extricate ourselves from fatalism,we at least need to reject one of the premises.Prior‘s position is that he accepts the ?necessity of the past‘ and rejects the ?principle of future excluded middle‘.Secondly,it classifies and discusses Prior‘s reconstruction for master argument.It points out that the second argument premise added by him presupposes time is discrete.Accordingly,the argument just holds conditionally.In the following,it introduces the linear time and the branching time.It points out that the discuss concerning the determinism and indeterminism of the future events is closely related to time structure and branching time is vital for the justification of the indeterminism view.Finally,it elaborates that Prior as well as some other scholars how to solve the problem of future contingency.In my opinion,in contrast with ?ukasiewicz‘s three-valued solution,Proir‘s Peircean solution and the true futurist theory,Proir‘s Ockhamist solution is relatively a good solution.The reasons are approximately as follows.(1)In order to insist on indeterminism,three-valued logic abandons the Principle of bivalence.However,according to tense and modal logic,we can equally hold on indeterminism on the basis of bivalence.Therefore,in line with Ockham‘s Razor,it is unnecessary to introduce the third value.(2)I believe that ?future contingent proposition‘ has truth-value now,but we as human do not know.(3)The past has been recorded and the present is beening experienced,they are unchangeable,however,the future is not,the kind of the progress of future events is much more than one.Hence,if time is branching,there are many routes into the future.?Future contingent proposition‘ was explained through different routes.The solution combines ?future contingent proposition‘ with modalities such as necessity and possibility etc.,which is consistent with common sense and natural language.(4)The true futurist theory is(at least now)no recommendation because of its complexity.The fourth chapter deals with Prior‘s views about time.Firstly,it considers Prior‘s analysis to McTaggart‘s time‘s A-series,B-series and the argument that time is unreal.In my opinion,McTaggart‘s argument that object the reality of tense is in fact based on a questioned assumption,ie.he illustrates ?has been‘,?is‘ and ?will be‘ which are temporal via ?is‘ non-temporal.In the following,it classifies Prior‘s ?present‘ concept and introduces the relevant criticism.The author argues that Prior‘s ?present‘ concept has been criticized because it can not explain change.Then,it mainly classifies Prior‘s discussion to Barcan formulas and deals with the relevant discussion.The Barcan formulas mean that there is the same individual domain in different time in tense logic,which goes against the picture of the real world.Therefore,in my opinion,we can reject Barcan formulas in tense logic.Finally,it classifies Prior‘s arguments about time‘s reality and relativity and analyzes and reviews them.The fifth chapter summarizes and looks forward to the thesis.The thesis as a whole affirms Prior‘s pioneering research in the field of tense logic,but some of his views can be criticized.The points of the innovation of the thesis are as follows.(1)It carefully analyzes Prior‘s theory that the ?four grades of tense-logical involvement‘ and then points out he characterizes the four grades with the way mixing syntax and semantics to argue the privileged status of tense.However,this research does not succeed.Because the construction of his logical systems(from the first grade to the fourth)is increasingly complex.The high-order hybrid logic of the fourth grade is in itself questionable.It is hard to find out its modal,not to mention to research its meta-logical properties.However,adopting the standard research method of tense logic is not only simple and clear,syntax and semantics are clear and it is easy to prove all kinds of meta-logical properties.It also clearly indicates that with regard to the logical research,A-concepts are more fundamental,however,it can be explained by B-concepts in semantics.The distinction between the four grades is neither reasonable nor necessary.(2)The thesis profoundly discusses Diodorus‘ master argument reconstructed by Prior formally and analyses other scholars‘ criticism to Prior's reconstruction.It points out that the argument premise added by him presupposes the discreteness of time.Therefore,the argument just holds conditionally.In regard to other scholars‘ criticism to the ambiguities of premises in his reconstruction,if we adopt the normative reading method of tense logic,they are completely eliminable.(3)The thesis considers Prior‘s and other scholars‘ solutions about the problem of future contingency.It points out that the discuss concerning the determinism and indeterminism of future events is closely related to the linear time and the branching time.The author argues that although there are disputes regarding the ontological status of the branching time,from a logical point of view,Proir‘s Ockhamist logic based on the branching time is a less problematic solution of dealing with the true theory of ?future contingent proposition‘.(4)The thesis classifies and evaluates Prior‘s views about time.It argued that Prior‘s view of time,ie.the tense view of time,is inspired by modal point of view.The way offered by modal logic is also the way characterizing time.Barcan formulas mean there is the same individual domain in different time in tense logic,which violates the actual picture of the real world.There can be the different things in different time in real world,which means that there can be different individual domain in different time.Hence we can reject Barcan formulas in tense logic.