Ultimate, eternal reality is the spiritual world. The spiritual world consists of a here-to-fore, a war within which every human is a soldier. The problem is that most humans have no idea that the spiritual world exists and of those who acknowledge its existence, few recognize the war.
As Bob Dylan sang, you're going to have to serve somebody. It may be the devil, or it may be the Lord, but you're going to have to serve somebody.
There is a constant battle and our minds are the battlefield. Satan puts ideas into our minds to battle the Holy Spirit and other Christians. We either listen and follow through with these ideas or we submit to the Holy Spirit and battle against the enemy. That's why Paul said, "For our struggle is not against flesh and blood, but against the rulers, against the powers, against the world forces of this darkness, against the spiritual forces of wickedness in the heavenly places." (
Ephesians 6:12)