Why a two-edged sword?

When someone says something is “a two-edged sword,” they are saying the concept has or can have both favorable and unfavorable results. Biblically, the sword is the word of God that changes hearts and minds (Romans 12:2). When yielded as a teaching tool, it produces right thinking and attitudes but, like a surgeon’s scalpel has to cut away the old, the 2-edged sword cuts out faulty thoughts and ideas that the brain (both spiritual and physical) has incorporated into the individual’s thoughts and attitudes.