1.  Paul’s argument in Eph. 4:17-10 is that once a person comes to know Jesus Christ as Savior they should no longer live the way they used to.  We should be changed, starting with out thinking.  As Warren Wiersbe put it:  “The whole outlook of a person changes when they trust Christ, including their values, goals, interpretation of life.”

2.  There is a heavy emphasis in this passage on “thinking, the mind, learning.”  In his book, Ordering Your Private World,” author Gordon MacDonald mentions five dangers of mentally out-of-shape Christians:

-“Mentally out of shape Christians are prey to falling victim to destructive ideas and systems.”

-“We must come to recognize that the race of life will have to be run on endurance and discipline and not talent.”

-“The pursuit of amusement (activity without thought) has supplanted the hard work of thinking in our society.”

-“The mind must be trained to think, to analyze, to innovate.”

-“We in the evangelical Christian world must appreciate the distinction between gatherers of details and rules and skilled handlers of truth.”

3.  The corrupted mind of the unbeliever leads him to darkened understanding (willful ignorance of God), to separation from the life of God, to a “petrified” heart which is insensitive to conscience, shame, and consideration of other people.