For when for the time ye ought to be teachers, ye have need that one teach you again which be the first principles of the oracles of God; and are become such as have need of milk, and not of strong meat. For every one that useth milk is unskilful in the word of righteousness: for he is a babe. But strong meat belongeth to them that are of full age, even those who by reason of use have their senses exercised to discern both good and evil. (Hebrews 5:12-14)

Familiarity can both dull or sharpen the senses. Someone who lives next to an airport or railroad can get so accustomed to the sound of planes and trains as to become oblivious to it. On the other hand, the FBI trains its agents to spot counterfeit currency by familiarizing themselves with the genuine. By becoming so familiar with the genuine, the counterfeit becomes easily detectable. 

As Christians, we should strive to desensitize ourselves to the familiar sounds of a spiritually distracting world. At the same time, we should so familiarize ourselves with the Word of truth that we’re able to easily detect error wherever it is found. Of course, all of this requires a continual sharpening of our spiritual senses on the “whetstone” of God’s Word.

Those Christians who are willing to hone themselves spiritually become spiritually mature. They are also far less likely to spiritually shortchange themselves by swapping God’s genuine truths for this world’s poor imitations. On the other hand, those Christians who are unskilful in their handling of the Scriptures are mere babes in Christ. Consequently, they are too immature for a solid spiritual diet, not to mention too immature to discern for themselves between “good and evil.”

“It is tragic that there are people who have been members of the church and saved for years, and they are still going around saying, ‘Goo, goo.’ They have nothing to contribute but little baby talk. All they want is to be burped periodically.” (J. Vernon McGee)