In this passage, Jesus is talking about having one unified perspective. The word “single” here can mean undivided, whole, or complete. Your perspective is good and healthy when your eye is single.
Let’s talk about our eyes more literally. What do we do when our eye isn’t single? What do you do when you’re having double vision, or you feel like the room is spinning?
Obviously, we’re not going to operate a motor vehicle or walk down a flight of stairs.
What we do, almost instinctively, is take hold of something stable. We close our eyes for a moment, let our perspective adjust, and then we can see clearly again.
Unfortunately, too many people live life trying to hold a variety of perspectives at the same time. The result is a life that could best be described as dizzy.
Now, why does Jesus say that the alternative to “single” is “evil?” Isn’t that a little harsh? Because having a divided perspective creates a life of selection, not a life of submission.
We decide what parts of our lives we’ll apply a biblical perspective to. Then God is no longer God, but a tool or strategy to fix some part of our life. And yes, that is evil.
How do we fall into a divided perspective? It could be at least two ways. First, we come to God just looking for help in a certain area of life. The second is we succumb to external pressure from people around us – “you can be a Christian, but don’t bring your Christian perspective into this relationship / workplace / family gathering, etc.”
James 1:8 says that a double-minded man is unstable in all his ways. Not some of his ways…all of them. And not just unsuccessful or unwise…unstable. That means even your faith perspective, when competing with other perspectives, will be unstable.
To grow as a disciple means we see things the way Jesus sees things. He says in John 8:12, "I am the light of the world; whoever follows me will not walk in darkness, but will have the light of life."
We should use his light to see things clearly.
That means we see ourselves from His perspective. We see others from his perspective. We see our family, our marriage, our work, and our church from his perspective. We even see God Himself from his perspective.
