In Christ's ministry a. In unbelievers a. In believers a. Demons are by nature the same kind of spirit beings as angels. They are personal, intelligent beings.
Demons have great intelligence.
They're knowledge is not infinite. They learned it through thousands of years of experience and observation. This activity is blatant in primitive cultures. Recommended Reading and References Fred Dickason, Angels, Elect and Evil. Moody Press, 1975.