As I know from firsthand experience, they exist, and we are all affected by them, whether we acknowledge them or not. Best to see them for what they are, how they impact our lives, and know how the Bible teaches us to deal with them. Saying Satan and his evil fallen angels don’t exist is the most dangerous course to take, because that gives them free reign over our lives. I made that mistake a one point in my life, and God allowed them to work a full measure of wickedness and grand deception on me, such that I would never again dare to even think that they are not all around us, looking for any opportunity to take us down. This is true for all humankind, but especially true for Christians. Those who don’t believe, Satan already possesses—it is the believers they desire to lead astray. They are most dangerous when they appear as angels of light, which they once were and are very capable of disguising themselves as now. It requires discernment, which only comes from knowledge of God’s word by the working of His Spirit in us, to distinguish the true from the false.