From Genesis to Revelation – and especially during the earthly life of Jesus – the Bible witnesses to the reality of evil supernatural beings who oppose God and seek the harm of his good creation.

In addition to this plain witness of Scripture, a number of other factors should be considered.

Clinton E. Arnold writes:

1. Science is inherently incapable of answering this question. Some critics grant science authority to make judgments on issues it is incapable of judging. Just as science is incompetent to adjudicate on morality, so it is also beyond its jurisdiction in trying to decide the question of demonic existence. Science seeks to describe and explain natural phenomena. There is no reason to assume it has power to answer questions regarding the supernatural, such as whether these beings exist.
2. Purely naturalistic explanations are not adequate for describing many forms of evil in the world. Although the impact of sin on the human soul explains much of the proliferation of evil, some situations are still so abhorrent or inexplicable that they suggest a demonic origin. The horrors of an Auschwitz or of a mother roasting her own child to death imply a powerful force leading humanity to destruction.
3. Some therapeutic situations are best explained by the work of a spirit being. While it is true that symptoms produced by schizophrenia, dissociation, and other psychological and chemical disorders have often been wrongly attributed to demons, some conditions are best explained by the direct influence of a spirit entity. The international community of mental health professionals recognizes this and labels it “Trance and Possession Disorder,” an especially common diagnosis in non-Western cultures.
4. We need to learn from the broader sweep of human history and cultures. The last 300 years in Western history represent the only time when the existence of evil spirits has been viewed with widespread skepticism. Furthermore, an exploration of other cultures throughout Asia, Africa, the Pacific Islands, and elsewhere reveals that belief in evil spirits continues to be integral to the worldview of many people groups.

Apologetics Study Bible, art. ‘Can We Still Believe in Demons Today?’ (Numbering added)