$ sudo pacman -S mutter
resolving dependencies...
looking for inter-conflicts...

Packages (1):

Name          New Version  Net Change

extra/mutter  3.12.2-1       6.88 MiB

Total Installed Size:   6.88 MiB

:: Proceed with installation? [Y/n] 
(1/1) checking keys in keyring                                                                 [########################################################] 100%
(1/1) checking package integrity                                                               [########################################################] 100%
(1/1) loading package files                                                                    [########################################################] 100%
(1/1) checking for file conflicts                                                              [########################################################] 100%
(1/1) checking available disk space                                                            [########################################################] 100%
(1/1) installing mutter                                                                        [########################################################] 100%

$ gnome-tweak-tool
WARNING : Shell not installed or running
WARNING : Error detecting shell
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/gtweak/tweaks/tweak_group_shell_extensions.py", line 278, in __init__
    raise Exception("Shell not running or DBus service not available")
Exception: Shell not running or DBus service not available
INFO    : GSetting missing org.gnome.nautilus.desktop
INFO    : GSetting missing org.gnome.nautilus.desktop
INFO    : GSetting missing org.gnome.nautilus.desktop
INFO    : GSetting missing org.gnome.nautilus.desktop
INFO    : GSetting missing org.gnome.nautilus.desktop
WARNING : Shell not running
None
INFO    : GSetting missing org.gnome.shell.calendar
INFO    : GSettings missing key org.gnome.settings-daemon.plugins.power (key lid-close-battery-action)
INFO    : GSettings missing key org.gnome.settings-daemon.plugins.power (key lid-close-ac-action)
INFO    : GSettings missing key org.gnome.settings-daemon.plugins.power (key lid-close-suspend-with-external-monitor)