If we have two eyes, it is so we can see with stereoscopic vision. Each eye sees a slightly different view to the other eye. Some things in central field of view are almost the same in each eye, but the slight difference of angel allows three dimensional vision signals to be put together in the brain by combining optic nerve vision from each eye, forming an impression of distance, or depth of view. Some things are quite different in each eye, such as at the edges of our range of vision. The one eye sees only one side of the nose. The other eye sees only the other side. The brain might filter out such things as being not very helpful and relevant, but sometimes the things we can see just with one eye and not the other are important for the brain to notice, such as an insect flying towards one eye. Stereo vision from two eyes tends to be better than vision from only one eye. Catching a ball coming towards us is easier with such stereo vision, for example.
I would see the New Testament in this way. In particular it gives us at least two main views of the person and teachings of Jesus Christ. There is the view of John. There is the view of Paul. Each had a slightly different audience. This affected what they wrote. To help our eyes tell our brains what is to be seen and to help two sets of vision information to be combined, the brain can focus on things seen similarly by each eye, such as things directly ahead in the centre of our field of view. Likewise there are passages of Paul and John which cover a very similar view of the teachings of Jesus. John’s gospel chapter 8, and other chapters such as chapters 1 and 3, overlap well with Paul’s epistle to the Ephesians especially chapters 1, 4 and 5. There are interesting differences. John speaks of believers being enabled to become sons/children of God. Paul speaks of believers being adopted as sons of God. John covers the teachings of Jesus on topics such as things that must be stopped, such as adultery, lying, murderously hating. Paul covers these too as teachings according to the truth found in Jesus, adding to these stealing. He calls it not stopping these things, but putting off of these things. Combining the views of these teachings gives us what we could regard as analogous to depth of vision and stereoscopic vision. Clearly they were describing the same teachings and the same truth.
Jesus Christ’s saying long puzzled me: “The eye is the lamp of the body.”
But we might say today that the eye has an optic nerve which tells the brain what we see, and telling the brain is effectively telling the body, so, yes, the eye is enlightening the body, as a lamp to the body.
He said: “The eye is the lamp of the body. If the eye is healthy, the whole body will be full of light.”
The apostles gave the light of the teachings of Christ to the body of Christ. If they were in good healthy spirit and mind in understanding his teachings, they would fill his disciples, members of his body, with light. And those of us reading their writings today can be filled with his light too.
