What does Mark 3:11 mean?
Mark chapter 3 describes the different reactions of people as they experience Jesus. So far, the Pharisees and Herodians have plotted to kill Him (Mark 3:6), and the common people have mobbed Him, looking for healing (Mark 3:7–10). Here, we learn about the reactions of the demons."Unclean" is a common word to describe something that is against the Mosaic Law, specifically against the ceremonial regulations. According to Jewish dietary law, things like pork and shellfish are unclean. Certain biological acts and diseases make people unclean until they either wash (Leviticus 11:25), complete a time of quarantine (Leviticus 11:24), and/or are healed (Leviticus 13).
An "unclean spirit," here, simply means a demon: a fallen angel. These beings are contrasted with God's angels who are clean. The unclean spirits here aren't just floating free, but are attached to people. The Bible doesn't go into too many specifics about demon possession. It appears to have been common in Christ's era, and some demons were responsible for physical or mental illnesses. Although Jesus could make the distinction between a demon and a physiological or psychological condition, He does not call us to do the same. Sometimes demon possession may be obvious. Most of the time, however, we should not expect that a demon is behind every illness.
Just as Jesus discerns demons, they know who He is. To call Him by His name seems to be a compulsion the demons can't help. In Mark 1:24, one of them calls Jesus "the Holy One of God." The people have faith that Jesus can heal them, but they don't treat Him with reverence. They push and crowd Him, trying to touch Him, to the point where He has to arrange for a boat in case things get dangerous (Mark 3:9). The demons, however, fall down before Him, acknowledging His identity and authority. They do not follow Him (James 2:19), but knowing who He is, they have no choice but to worship and fear Him. This same fear keeps Christ-followers safe from demon possession.
