•  132
    Do Time Travelers Suffer from Paradoxes?
    Annals of the Japan Association for Philosophy of Science 15 (2): 95-98. 2007.
    In this paper I give consideration to some apparent impossibilities for the time travelers to the past. After criticizing the views of D. Lewis and K. Vihvelin, I will show in what sense they are really impossible.
  •  123
    Four Kinds of Boundary : From an Ontological Point of View
    Interdisciplinary Ontology 2 87-90. 2009.
    Casati and Varzi have developed a theory of boundary based on extensional mereotopology and the distinction between fiat and bona fide boundaries. Firstly, I point out some problems in their theory that are related to the contact of bodies. Next, I propose a way of classification of boundaries into four kinds based on substance ontology and an alternative distinction between potential and actual boundaries. Finally, I will show that my way of classification makes it possible to solve the problem…Read more
  •  142
    The Power of Holes
    Ontology Meeting: A Supplementary Volume for 2011, February Meeting 7-11. 2011.
    Firstly I define a hole as a dependent matter-less endurant, which is a little modification of Casati and Varzi’s definition. Adopting this definition, holes seem to invite three problems about causation: (1)causal closure, (2)ungrounded disposition and (3)causal overdetermination. I will defend my definition against all these problems by showing that holes are limiting cases of physical endurants rather than their opposition and that they have causal powers in a broad sense.
  •  13
    Partial Logic as a Logic of Extensional Alethic Modality
    Journal of the Japan Association for Philosophy of Science 34 (2): 61-70. 2007.
    In my paper 'Validity in Simple Partial Logic'(2002) I made comparison between several definitions of validity in Simple Partial Logic(SPL) and adopted two of them as most appropriate. In this paper, after elaborating more on these two definitions than in my previous paper and considering the characteristics of Partial Semantics, in which these definitions are given, I construct a tableau proof system and prove its soundness and completeness. Then, based on the characterization of Partial Semant…Read more
  •  108
    Serious Copula-Tensing
    Interdisciplinary Ontology 5 67-73. 2012.
    M. Johnston proposed an adverbialist solution to the problem of intrinsic change for enduring things. D. Lewis interpreted it as a way of tensing the copula. In his view, it has the defect of replacing the having simpliciter of a property by the standing in a triadic relation to a property and a time, and so is threatened by Bradley’s Regress. I agree with Lewis on requiring the having a property to be non-relational, while I disagree with him on restricting it to the having simpliciter. I tense…Read more
  •  233
    Łukasiewicz has often been criticized for his motive for inventing his three-valued logic, namely the avoidance of determinism. First of all, I want to show that almost all of the critcism along this line was wrong. Second I will indicate that he made mistakes, however, in constructing his system, because he had other motives at the same time. Finally I will propose some modification of his system and its interpretation which can attain his original purpose in some sense.
  •  115
    Validity in Simple Partial Logic
    Annals of the Japan Association for Philosophy of Science 10 (4): 139-153. 2002.
    Firstly I characterize Simple Partial Logic (SPL) as the generalization and extension of a certain two-valued logic. Based on the characterization I present two definitions of validity in SPL. Finally I show that given my characterization these two definitions are more appropriate than other definitions that have been prevalent, since both have some desirable semantic properties that the others lack.
  •  168
    Tensed Ontology Based on Simple Partial Logic
    Proceedings of Ninth International Symposium on Temporal Representation and Reasoning: TIME-02 141-145. 2002.
    Simple partial logic (=SPL) is, broadly speaking, an extensional logic which allows for the truth-value gap. First I give a system of propositional SPL by partializing classical logic, as well as extending it with several non-classical truth-functional operators. Second I show a way based on SPL to construct a system of tensed ontology, by representing tensed statements as two kinds of necessary statements in a linear model that consists of the present and future worlds. Finally I compare that w…Read more
  •  134
    Bourne on future contingents and three-valued logic
    Logic and Logical Philosophy 18 (1): 33-43. 2009.
    Recently, Bourne constructed a system of three-valued logic that he supposed to replace Łukasiewicz’s three-valued logic in view of the problems of future contingents. In this paper, I will show first that Bourne’s system makes no improvement to Łukasiewicz’s system. However, finding some good motivations and lessons in his attempt, next I will suggest a better way of achieving his original goal in some sense. The crucial part of my way lies in reconsidering the significance of the intermediate …Read more
  •  93
    The Ontology of Many-Worlds : Modality and Time
    The Paideia Archive: Twentieth World Congress of Philosophy 13 42-46. 1998.
    There are two types of theories regarding many worlds: one is modal, while the other is temporal. The former regards reality as consisting of many possible worlds, while the latter holds that reality consists of many momentary worlds, which are usually called moments. I compare these two theories, paying close attention to the concept of transworld identity and compare trans-possible world identity with trans-momentary world identity (or transmoment identity). I characterize time from the point …Read more