what do christians (and people in general) mean by "feeling empty inside"?

[bladevalant546]

I like your formula, which is why I like Zen Buddhism the best as most of their tenets are more about actually improving the human condition instead of glorifying it and outright shoot the responsibility off the individual. According to typical human psychology negative emotions are the most powerful or atleast easiest to manipulate. Guilt being one of these negative emotions is often used in tandem with fear to bring in followers.

Now this is not meaning all religions utilize this for means of control and/or power or money. This is however the main tool most will use to those ends. Cults and political religions often utilize fear and guilt as their methods of control. What these two emotions especially guilt generates false insecurity (which is your empty space). Often times will use generalized statements like; "Someone here is struggling with pornography, or someone is struggling against lust, or my favorite someone is doubting God and you are waiting for a sign." These are very common statements that alot of people could apply themselves too. Couple that with the fear of pain (torture in hell) that makes for a powerful means of psychological manipulation.

Basically in short it is a sad thing because certain religions have such huge potential of bring peace and tolerance to certain aspects of humanity.
(sorry for long winded response, but I thought hard about what you wrote :p)