In earlier times an army would poison their own wells so that an invading army couldn’t use them. This turned into a metaphor for biasing the mind against something. We can poison our own mind if we’re not careful. We allow the lies of the world, the flesh, and the Devil to turn us against God. Sometimes without even realizing it. This is essentially what the Devil did to Eve in the Garden. Satan poisoned the well of her because she allowed him to fill it with lies. The result was that eventually she didn’t trust God. It was acid to her faith. Such a condition is still a threat to believers today, so Paul provides the antidote in Philippians 4:8. He begins with words of friendliness, “Finally, brothers” and then proceeds to give an eight-part prescription for maintaining spiritual mental health. Looking to the end of the verse we see the dominant imperative verb. This is the answer to how we get there. He says, “think”. This is a goal and an activity. It comprises the reward, and ultimately the cultivation of a useful mind.