Singer songwriter Ray LaMontagne should be on your iPod. In his latest release (Live Sessions EP) he has a song titled "Empty" that includes these lyrics:

There's a lot of things that can kill a man, 
   There's a lot of ways to die.
And there's some already dead that walk beside me.

As LaMontagne looks around he sees people that are so estranged, confused and despairing that he can only describe them as the walking dead.

The song reminds me of Ephesians 2:1-2 where the Apostle Paul rehearses who we are apart from Christ:

And you were dead in your trespasses and sins in which you once walked, following the course of this world, following the prince of the power of the air, the spirit that is now at work in the sons of disobedience (ESV).

Indeed, apart from faith in Christ we are among the walking dead--spiritually dead human beings without any pulse for God. This reality should humble us and promote praise to the One who gave us life.

What do I see when I walk the streets of my city?