<div dir="ltr"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small;color:#000000">Nick,</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small;color:#000000"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small;color:#000000">One of the most attractive things about your posts is how charming they are. They are so well written! Thank you for keeping the discussion at such a civilized and enjoyable level -- even when I don't agree with you.</div><div><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><font><u style="color:rgb(33,33,33);font-family:"Helvetica Neue",Helvetica,Arial,sans-serif;font-size:16.5px;line-height:20px"><br></u></font></div><div dir="ltr"><font><u style="color:rgb(33,33,33);font-family:"Helvetica Neue",Helvetica,Arial,sans-serif;font-size:16.5px;line-height:20px"> </u></font><span style="color:rgb(33,33,33);font-family:"Helvetica Neue",Helvetica,Arial,sans-serif;font-size:16.5px;line-height:24.75px"> </span>-- Russ Abbott <br>Professor, Computer Science<br>California State University, Los Angeles<br></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div><br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Sat, Apr 27, 2019 at 9:44 AM <<a href="mailto:lrudolph@meganet.net">lrudolph@meganet.net</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Frank writes:<br>
> I would hate to have to demonstrate that a modern computer is an instance<br>
> of a Turing Machine. Among other things they usually have multiple<br>
> processors as well as memory hierarchies. But I suppose it could be done,<br>
> theoretically.<br>
<br>
First a passage from a chapter I contributed to a book edited by a<br>
graduate student Nick knows (Zack Beckstead); I have cut out a bit in the<br>
middle which aims at a different point not under consideration here.<br>
===begin===<br>
If talk of “machines” in the context of the human sciences seems out of<br>
place, note that Turing (1936) actually introduces his “automatic machine”<br>
as a formalization (thoroughly mathematical, though described in<br>
suggestive mechanistic terms like “tape” and “scanning”) of “an idealized<br>
*human* calculating agent” (Soare, 1996, p. 291; italics in the original),<br>
called by Turing a “computer”. [...] As Turing remarks, “It is always<br>
possible for the computer to break off from his work, to go away and<br>
forget all about it, and later to come back and go on with it” (1936, p.<br>
253). It seems to me that then it must also be “always possible for the<br>
computer to break off” and never “come back” (in fact, this often happens<br>
in the lives, and invariably upon the deaths, of non-idealized human<br>
calculating agents).<br>
===end===<br>
Of course Turing's idealization of "an idealized *human* calculating<br>
agent" also idealizes away the fact that human computers sometimes make<br>
errors. A Turing machine doesn't make errors. But both the processors and<br>
the memory of a modern computer can, and *must* make errors (however<br>
rarely, and however good the error-detection). To at least that extent,<br>
then, they are not *perfect* instantiations of Turing machines. On the<br>
other hand, that very fact about them makes them (in some sense) *more*<br>
like (actual) human calculating agents.<br>
<br>
So, Nick, why are you asking what Turing machines think, instead of what<br>
modern computers think? (Be careful how you answer that...)<br>
<br>
<br>
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