Romans 8:6a says that the mind set on the flesh is death. Life is the issue of the spirit; death is the issue of the flesh. Death comes out of the flesh.
The sense of death causes us to know the things of the flesh. We know death because we have the feeling, the consciousness, of death. The inner feelings of dissatisfaction, emptiness, oldness, dryness, darkness, and depression are aspects of the sense of death versus the sense of life. Also, the inner feelings of strife, discord, discomfort, restlessness, pain, bondage, and grief are aspects of the sense of death versus the sense of peace.
By these four things—life, law, peace, and death—we can realize the sense of the spirit. Then by the sense of the spirit, we can know the spirit. The spirit may be likened to electricity. No one can see it. It can only be realized by its issue. We know electricity is present in a room because of the lights in a room. The spirit is the same. No one can see the spirit, but with the spirit there are many issues, such as the issue of life, the issue of the law, the issue of peace, and the issue of death. Death is a negative issue, the issue on the negative side to point us to something on the positive side. By the consciousness of life, the consciousness of the law, the consciousness of peace, and the consciousness of death, we can sense the spirit. We can know the spirit by the sense of the spirit.