There is a clear belief in the New Testament that there is a spiritual and physical realm, and that both interpenetrate the other. There are things seen and unseen. Today it is not considered silly to believe that there are tiny little invisible entities at work in our bodies and environment to destroy us (germs, viruses). Nor is it silly to believe that there are invisible forces at work which control our thoughts and affect our feelings (peer pressure, beliefs, relationships, music). Invisible things are real, we know that. We can even measure their impact (how beliefs impact health, how peers impact values and choices).
Sometimes these invisible, unseen things work for good (digestion and kindness) sometimes they are malicious (flu and prejudices) and sometimes they are deadly (ebola and riots).
Science and social science have progressed our insights and knowledge, but their scope is limited. There is also a spiritual realm, a realm also unseen and unseeable. A realm with measurable impact but it is not measured, weighed or see with physical instruments. It is the realm which Jesus also addressed in healing and forgiving (Saving) people. He fixed them physically and conquered illness and disease, He mended relationships and reconciled people (to God and one another) and He also declared His power over the demonic. Satan is invisible and unseen, but He is real. If we over emphasize the devil we are in error. The personal (called the flesh) beliefs and choices we make account for lots of things. Our mental, emotional and spiritual character and choices are our own fault. We must change how we believe, how we think, what we eat, how we live, who we spend time with, what we read, how we pray, etc. It is our choice and we need a DISCIPLE life style (disciplined). We must also understand that the world has its own set of powers and authorities. We must work in our communities to promote human values and justice. We must fight injustice and inhumanity. Because, human beings and human institutions (which are bigger than humans) also are at odds with God and His rule. Our families, communities, nations, and all places of work and play exert influence, even control, over us. The evil at work in 'the world' is real and powerful. Jesus confronted that when He died, as well. The power of religious institutions and secular (Temple and Empire) killed Jesus just as individuals (Judas, priest, Pilate, etc.) made choices. Jesus' death revealed the evil in our hearts and in our world/institutions. He also conquered them by forgiving us from the cross we nailed Him to.
But the spiritual realm was also in play. Satan was working with cooperative sinful humans and cooperative sinful institutions. There was a spirit warfare as well. A war fought in the realm of angels and demons, darkness and light, demonic spirits and The Holy Spirit. The battle was won through Jesus (His incarnation, faithful life of obedience, His ministry of proclaiming God's rule and healing, exorcising, reconciling, teaching; through His death, resurrection and ascension, through His rule from the spiritual realm and finally, when He comes back, through His physical rule in the New Heaven and New Earth; until then, now, through the Holy Spirit, God among us today in divine breath/wind/spirit).
Most Christians tend to minimize the spiritual warfare. I know I can ignore the unseen. But does unbelief in evil spirits somehow impact our ability to receive the Holy Spirit? Does negating the spiritual lead us to beliefs which reduce us to animals (only physical) helpless and hopeless to our physical impulses and the powerful institutions which rule us? Don't beliefs impact our bodies? Don't we see that believing and not believing have impact?
Twice I have looked up a Bible verse on my phone the past week. Each time the first entry on my google was from an atheist website. Atheist!!! This is the work of persons and institutions. Yet, I think there is also more. Anyone using the search engine would be led to a commentator who does not believe in God when looking at this verse. NOT the largest church in the world (Roman Catholic) nor the oldest (Eastern Orthodox). Not the group which emphasizes the Bible alone (Evangelical). Not people who treasure what it says, who translated the texts and make them available in our language (all Christians and churches). No, the first place you are taken is to someone who will say "there is no God." Someone who does not believe.... Let that sink in a moment and tell me that there is no war with Satan. The war with the demonic has been won, but the battles continue. Jesus continues, in and through the church, to conquer the world, the flesh, and, yes, the devil. We are His soldiers in that war (or doctors, or healers, or bringers of light, or repairmen, or whatever image you prefer to describe this process of ongoing salvation). We are his team, and we need to understand we are playing hardball. The enemy is clear about that, the enemy is going all out to bring sickness, death, violence, conflict, despair and misery. The enemy is sowing fear, doubt, unbelief. The enemy (flesh, world and, yes, the devil) is all about taking away hope and joy.
Jesus is the Victor (for those who watched the World Series, He is Madison Bumgarner times infinity). Jesus is playing hard ball. For love of the Father and love of His creation and His people. Jesus is serious, even unto death on a cross. Will you play hardball for Him and with Him?