<!DOCTYPE html><HTML lang="en"> <head><meta charset="utf-8"> <title>Dowe (Phil) - The Case for Time Travel (Theo Todman's Book Collection - Paper Abstracts) </title> <link href="../../TheosStyle.css" rel="stylesheet" type="text/css"><link rel="shortcut icon" href="../../TT_ICO.png" /></head> <BODY> <CENTER> <div id="header"><HR><h1>Theo Todman's Web Page - Paper Abstracts</h1><HR></div><A name="Top"></A> <TABLE class = "Bridge" WIDTH=950> <tr><th><A HREF = "../../PaperSummaries/PaperSummary_20/PaperSummary_20897.htm">The Case for Time Travel</A></th></tr> <tr><th><A HREF = "../../Authors/D/Author_Dowe (Phil).htm">Dowe (Phil)</a></th></tr> <tr><th>Source: Philosophy, Vol. 75, No. 293 (Jul., 2000), pp. 441-451</th></tr> <tr><th>Paper - Abstract</th></tr> </TABLE> </CENTER> <P><CENTER><TABLE class = "Bridge" WIDTH=800><tr><td><A HREF = "../../PaperSummaries/PaperSummary_20/PaperSummary_20897.htm">Paper Summary</A></td><td><A HREF = "../../PaperSummaries/PaperSummary_20/PaperCitings_20897.htm">Books / Papers Citing this Paper</A></td><td><A HREF = "../../PaperSummaries/PaperSummary_20/PapersToNotes_20897.htm">Notes Citing this Paper</A></td><td><A HREF="#ColourConventions">Text Colour-Conventions</a></td></tr></TABLE></CENTER></P> <hr><P><FONT COLOR = "0000FF"><U>Author s Introduction</U><FONT COLOR = "800080"><ol type="1"><li>What is <a name="1"></a><A HREF="../../Notes/Notes_11/Notes_1133.htm">time travel</A><SUP>1</SUP>? Intuitively, the idea is simple enough to have dominated science fiction books, movies and TV throughout the twentieth century. But defining <a name="2"></a><A HREF="../../Notes/Notes_11/Notes_1133.htm">time travel</A><SUP>2</SUP> is not simple. According to Paul Davies <a name="3"></a><A HREF="../../Notes/Notes_11/Notes_1133.htm">time travel</A><SUP>3</SUP> is travel to other times, just as we travel spatially to other <U><A HREF="#On-Page_Link_P20897_4">places</A></U><SUB>4</SUB><a name="On-Page_Return_P20897_4"></A>. No doubt this is right, but spelling out the analogy is not as straightforward as it may at first seem (try defining space travel, then exchanging 'time' for 'place' in the definition.) </li><li>However, one way to define <a name="4"></a><A HREF="../../Notes/Notes_11/Notes_1133.htm">time travel</A><SUP>5</SUP> is via the notion of a <em>causal process</em>. The simplest case of a causal process is the trajectory of a particle through time, where we think of the earlier stages of the particle as the cause of later stages. The same can be said for the history of a person  one's earlier stages are (partly) responsible for one's later stages. A full stomach causes nourishment, earlier perceptions are the cause of later memories, and so on. <a name="5"></a><A HREF="../../Notes/Notes_11/Notes_1133.htm">Time travel</A><SUP>6</SUP> is where a causal process connects two times in a special way. Dr Who's body is a causal process, and when the Tardis takes him from 1976 to 1876 that causal process connects two times in a special way. I say 'special way' to distinguish <a name="6"></a><A HREF="../../Notes/Notes_11/Notes_1133.htm">time travel</A><SUP>7</SUP> from the normal causal process, such as John's life, a causal process, connecting 1965 and 2005, the dates of his birth and death. </li><li>Following David Lewis, we can say that a causal process connects two times in a special way when the 'personal' time defined by the causal process is at odds with 'external' <U><A HREF="#On-Page_Link_P20897_8">time</A></U><SUB>8</SUB><a name="On-Page_Return_P20897_8"></A>. As measured by his watch, or digestive processes, Dr Who's trip takes 2 hours, let's say, which is at odds with the external time of minus 100 years. In the case of normal causal processes such as John's life, the personal time and external time coincide, so that is not <a name="7"></a><A HREF="../../Notes/Notes_11/Notes_1133.htm">time travel</A><SUP>9</SUP>. So we can say that <a name="8"></a><A HREF="../../Notes/Notes_11/Notes_1133.htm">time travel</A><SUP>10</SUP> is where a causal process connects two times in a way that involves a temporal <U><A HREF="#On-Page_Link_P20897_11">discrepancy</A></U><SUB>11</SUB><a name="On-Page_Return_P20897_11"></A>. </li><li>This idea of <a name="9"></a><A HREF="../../Notes/Notes_11/Notes_1133.htm">time travel</A><SUP>12</SUP> has long given philosophers difficulties. Most recently, in his paper 'Troubles with <a name="10"></a><A HREF="../../Notes/Notes_11/Notes_1133.htm">Time Travel</A><SUP>13</SUP>' William Grey presents a number of objections to <a name="11"></a><A HREF="../../Notes/Notes_11/Notes_1133.htm">time travel</A><SUP>14</SUP>, some well-known in the philosophical literature, others quite <U><A HREF="#On-Page_Link_P20897_15">novel</A></U><SUB>15</SUB><a name="On-Page_Return_P20897_15"></A>. In particular Grey's 'no destinations' and 'double occupation' objections I take to be original, while what I will call the 'times paradox' and the 'possibility restriction argument' are versions of well-known objections. I show how each of these can be answered, thereby defending the plausibility of <a name="12"></a><A HREF="../../Notes/Notes_11/Notes_1133.htm">time travel</A><SUP>16</SUP>. </li></ol></FONT><BR><HR><BR><U><B>In-Page Footnotes</U></B><a name="On-Page_Link_P20897_4"></A><BR><BR><U><A HREF="#On-Page_Return_P20897_4"><B>Footnote 4</B></A></U>: See <a name="17"></a>"<A HREF = "../../BookSummaries/BookSummary_06/BookPaperAbstracts/BookPaperAbstracts_6346.htm">Davies (Paul C.W.) - About Time: Einstein's Unfinished Revolution</A>", p. 234. <a name="On-Page_Link_P20897_8"></A><BR><BR><U><A HREF="#On-Page_Return_P20897_8"><B>Footnote 8</B></A></U>: See pp. <a name="15"></a>"<A HREF = "../../Abstracts/Abstract_00/Abstract_58.htm">Lewis (David) - The Paradoxes of Time Travel</A>", pp. 67-68 (of <a name="18"></a>"<A HREF = "../../BookSummaries/BookSummary_00/BookPaperAbstracts/BookPaperAbstracts_37.htm">Lewis (David) - Philosophical Papers Volume II</A>"). <a name="On-Page_Link_P20897_11"></A><BR><BR><U><A HREF="#On-Page_Return_P20897_11"><B>Footnote 11</B></A></U>: <ul type="disc"><li><FONT COLOR = "800080">Lewis' notion of a temporal discrepancy, by itself, without the notion a causal process, will not suffice as a definition of <a name="13"></a><A HREF="../../Notes/Notes_11/Notes_1133.htm">time travel</a> because it will count cases of closed timelike curves, discussed below, as <a name="14"></a><A HREF="../../Notes/Notes_11/Notes_1133.htm">time travel</a> even if nothing travels. </FONT></li></ul><a name="On-Page_Link_P20897_15"></A><U><A HREF="#On-Page_Return_P20897_15"><B>Footnote 15</B></A></U>: See <a name="16"></a>"<A HREF = "../../Abstracts/Abstract_00/Abstract_482.htm">Grey (William) - Troubles with Time Travel</A>". <BR><BR><FONT COLOR = "0000FF"><HR></P><a name="ColourConventions"></a><p><b>Text Colour Conventions (see <A HREF="../../Notes/Notes_10/Notes_1025.htm">disclaimer</a>)</b></p><OL TYPE="1"><LI><FONT COLOR = "0000FF">Blue</FONT>: Text by me; &copy; Theo Todman, 2018</li><LI><FONT COLOR = "800080">Mauve</FONT>: Text by correspondent(s) or other author(s); &copy; the author(s)</li></OL> <BR><HR><BR><CENTER> <TABLE class = "Bridge" WIDTH=950> <TR><TD WIDTH="30%">&copy; Theo Todman, June 2007 - August 2018.</TD> <TD WIDTH="40%">Please address any comments on this page to <A HREF="mailto:theo@theotodman.com">theo@theotodman.com</A>.</TD> <TD WIDTH="30%">File output: <time datetime="2018-08-02T09:27" pubdate>02/08/2018 09:27:47</time> <br><A HREF="../../Notes/Notes_10/Notes_1010.htm">Website Maintenance Dashboard</A></TD></TR> <TD WIDTH="30%"><A HREF="#Top">Return to Top of this Page</A></TD> <TD WIDTH="40%"><A HREF="../../Notes/Notes_11/Notes_1140.htm">Return to Theo Todman's Philosophy Page</A></TD> <TD WIDTH="30%"><A HREF="../../index.htm">Return to Theo Todman's Home Page</A></TD> </TR></TABLE></CENTER><HR> </BODY> </HTML>