All of us have a blind spot in regard to ourselves—it’s part of the human condition. There are things about ourselves, both good and bad, that we simply don’t see (Psalm 19:12 speaks to the bad). Other people, perhaps many, are aware of these things but we’re not. So it’s best to have a spirit of humility and not take ourselves too seriously. The worst situation is one where we have a blind spot in regard to our blind spot (John 9:41).
This appears to have been exactly the case with the bulk of the church at Sardis (Revelation 3:1-6).
Sardis was perched 1,500 feet high atop a ridge that was part of Mount Tmolus (elevation 5,800 feet). The path from the mountain down to the ridge (from the south), was the only way of approach to the city. The other three sides were sheer walls of rock, almost perpendicular to the valley below. The people of Sardis carefully guarded the southern pass but didn’t worry about being approached from any other direction. The city gained a reputation of being invulnerable to outside attack and they gloried in that status.
In the middle of the sixth century B.C., the Lydian kingdom (with Sardis as its capital), thrived under a king named Croesus. After subduing the Greek cities to the west, Croesus moved east and attacked Cyrus and the Persians at Pteria. He was unsuccessful and retreated to Sardis for the winter, dismissing his troops until spring. He then found out that Cyrus had followed him back and had massed his troops on the nearby plains. Croesus remained confident because he had called for reinforcements and knew he would be safe atop Sardis until they arrived. But according to Herodotus, when Croesus awoke the next morning, Sardis was overrun with Persians and the Lydian kingdom was no more.
Although the walls of Sardis were sheer, erosion had marked them with tiny cracks and crevices that served as footholds for the Persian soldiers. These pockets could easily have been filled in or smoothed flat by the Lydians, but they mistakenly assumed the three sides were unapproachable and didn’t even bother to post guards, much less inspect the terrain. The Persians crept into to Sardis like a thief in the night. And this happened not once but twice as three hundred years later the Seleucids under Antiochus III used the same tactic to capture the city again. They thought they were alive but they were dead!