I did an object lesson once in a men’s group that illustrated this principle. We started with a small cup full of water and talked about how the clear water in the cup represented our minds as God created them.
Unfortunately, we allowed the vile and the vulgar to get beyond our gates. (I recognize that for some of us, this was involuntary at first, but at some point, we began making our own decisions about what to allow in our gates.) I demonstrated this by dropping in some red flood coloring and giving examples of the types of things we allowed in (sexual images, lyrics, sounds, text and fantasies). With each drop, the water became murkier and murkier until it was dark with the sin.
As discouraging as it is to realize how we have damaged the purity of the gift of our minds, there is hope. As we think about true, noble, right, pure, lovely, admirable, excellent and praiseworthy things, God dilutes the negative effects of the garbage in our head (this was demonstrated by pouring in fresh water). Unfortunately, it takes much more water to purify the murky water than it does food coloring to darken it.
The hard fact is that walking in sexual purity is difficult and a life-long struggle. The good news is that it gets relatively easier the more we dilute the vile and vulgar that we’ve let in our gates. Satan can still call up old images, but we are stronger, and the struggle to “ferret out criminals and free the city of the LORD from their grip” becomes easier.
