Careful: chmod -X also looks for any existing exec bits:
$ umask 0
$ >foo >bar
$ ls -al foo bar
-rw-rw-rw- 1 user group 0 Sep 10 00:00 bar
-rw-rw-rw- 1 user group 0 Sep 10 00:00 foo
$ chmod o+x foo
$ ls -al foo bar
-rw-rw-rw- 1 user group 0 Sep 10 00:00 bar
-rw-rw-rwx 1 user group 0 Sep 10 00:00 foo
$ chmod u=rwX,g=rX,o=rX foo bar
$ ls -al foo bar
-rw-r--r-- 1 user group 0 Sep 10 00:00 bar
-rwxr-xr-x 1 user group 0 Sep 10 00:00 foo
I can choose to do a thing that I neither want nor have to do. I can also choose to not do a thing that I want or need to do. Can I prove that to you though? Does my desire to be contrarian countermand my free will? It very well might.
I can rewind a video and watch it again. That is no different from your time travel example. I don't think we can convincingly argue either way if a quantum field collapse will always happen the same way, even if we were to start save-scumming reality. I kind of hope we will never be able to.
None of this precludes me from having free will in the present. I don't even think I need quantum dice contently rolling around in my consciousness. Even if I am completely deterministic, I can still make choices. My brain is a computational device made of meat. I can only have so much faith in what a choice even means, but I sure think I know one when I see one.
I like the way you think! Too bad a I replied to a seaming empty post some 26 min after you. I always disliked this about Reddit. Seeing someone rewording the top reply for karma.
You may want to learn about the shell's "history expantion" functions. as an example:
~$ ls ~/Documents/taxes/tax_year_2012/2012-12-01.txt
/home/tom/Documents/taxes/tax_year_2012/2012-12-01.txt
~$ cd !!$:h
cd ~/Documents/taxes/tax_year_2012
~/Documents/tax_2012$ pwd
/home/tom/Documents/taxes/tax_year_2012
Here the string "!!$:h" is basically the last command's [ !! ] last argument [$], stripped of its last path component [:h].
You can actually do
chmod +777,u+rwx,go-w footo make the logic easier if you want to force a starting assumption.