MacBook Air shuts down when I close it

Question

Whenever I close my MacBook, it shuts down instead of going into sleep mode. At first, I thought it was a problem with my MacBook not waking up from sleep at all, but if I use the Sleep function from the drop down menu, it will wake up normally.
I've looked around the community to see if anyone had a similar issue, but most people say they need to reboot it to start it up again, which isn't my case at all. It just does a typical shut down. How do I make it go to sleep instead of shutting down when I close it?

Answer 1

Triple-click anywhere in the line below to select it:
bzgrep 'Previous Shutdown' /var/log/system.log*
Copy the selected text to the Clipboard (command-C).
Launch the Terminal application in any of the following ways:
☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)
☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.
☞ Open LaunchPad. Click Utilities, then Terminal in the icon grid.
Paste into the Terminal window (command-V).
Post any lines of output that appear below what you entered — the text, please, not a screenshot.