There is an extensive literature on time travel in both philosophy and physics. Part of the great interest of the topic stems from the fact that reasons have been given both for thinking that time travel is physically possible—and for thinking that it is logically impossible! This entry deals primarily with philosophical issues; issues related to the physics of time travel are covered in the separate entries on time travel and modern physics and time machines. We begin with the definitional (...) question: what is time travel? We then turn to the major objection to the possibility of backwards time travel: the Grandfather paradox. Next, issues concerning causation are discussed—and then, issues in the metaphysics of time and change. We end with a discussion of the question why, if backwards time travel will ever occur, we have not been visited by time travellers from the future. (shrink)

In an earlier paper I argued that time travellers cannot change the past: alleged models of changing the past either fall into contradiction or else involve avoiding, not changing, the past. Goddu has responded to my argument, maintaining that his hypertime model involves time travellers changing (not avoiding) the past. In the present paper I first discuss what would be required to substantiate the claim that a given model involves changing rather than avoiding the past. I then consider Goddu's hypertime (...) model and an earlier model due to Meiland. I argue that neither author does what would be required to substantiate the claim that the model involves changing (not avoiding) the past. I go on to give reasons for the stronger claim that no-one can present a coherent model and also substantiate the claim that it involves changing (not avoiding) the past. (shrink)

In this comment to Kehrer (2014) the relevance of atheistic argumentation in the domain of ethics as an important part of religion is sketched.

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In the context of classical (crisp, precise) sets, there is a familiar connection between the notions of counting, ordering and cardinality. When it comes to vague collections, the connection has not been kept in central focus: there have been numerous proposals regarding the cardinality of vague collections, but these proposals have tended to be discussed in isolation from issues of counting and ordering. My main concern in this paper is to draw focus back onto the connection between these notions. I (...) propose a natural generalisation to the vague case of the familiar process of counting precise collections. I then discuss the relationships between this process of counting and various notions of ordering and cardinality for vague sets. Some existing views concerning the cardinality of vague collections fit better than others with my proposal about how to count the members of such a collection. In particular, the idea that we should approach cardinality via certain formulas of a logical language -- which has been prominent in the recent literature -- is less attractive than other existing proposals. (shrink)

In his concept of an anthropological physiology, F.J.J. Buytendijk has tried to lay down the theoretical and scientific foundations for an anthropologically-oriented medicine. The aim of anthropological physiology is to demonstrate, empirically, what being specifically human is in the most elementary physiological functions. This article contains a sketch of Buytendijk''s life and work, an overview of his philosophical-anthropological presuppositions, an outline of his idea of an anthropological physiology and medicine, and a discussion of some episternological and methodological problems. It is (...) demonstrated that Buytendijk''s design of an anthropological physiology is fragmentary and programmatic and that his methodology offers few points of contact for specific anthropological experimental research.Notwithstanding, it is argued that Buytendijk''s description of the subjective, animated body forms a pre-eminent point of reference for all research in physiology and psychology in which the specific human aspect is not ignored beforehand. (shrink)