$ dpkg -l enlightenment
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Installed/Config-files/Unpacked/Failed-config/Half-installed
|/ Err?=(none)/Hold/Reinst-required/X=both-problems (Status,Err: uppercase=bad)
||/ Name                    Version                 Description
+++-=======================-=======================-==============================================================
pn  enlightenment           <none>                  (no description available)

$ sudo apt-cache policy enlightenment
enlightenment:
  Installed: (none)
  Candidate: (none)
  Package pin: (not found)
  Version table:
     1:0.16.7.2-1 999
        500 http://mirrors.kernel.org stable/main Packages
        500 http://mirrors.kernel.org testing/main Packages
         90 http://mirrors.kernel.org unstable/main Packages

$ sudo aptitude install enlightenment
Reading package lists... Done
Building dependency tree... Done
Reading extended state information
Initializing package states... Done
Reading task descriptions... Done
No candidate version found for enlightenment
No packages will be installed, upgraded, or removed.
0 packages upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Need to get 0B of archives. After unpacking 0B will be used.
Writing extended state information... Done
Reading package lists... Done
Building dependency tree... Done
Reading extended state information
Initializing package states... Done
Reading task descriptions... Done

$ sudo apt-get install enlightenment
Reading package lists... Done
Building dependency tree... Done
Package enlightenment is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
However the following packages replace it:
  enlightenment-data
E: Package enlightenment has no installation candidate