Are the old and new nature at odds with each other?
The old nature and the new nature are at total odds, constantly at war with each other. The old nature declares war on the new, and the new nature declares war on the old. They cannot agree on anything because their values are completely opposite, resulting in continual spiritual warfare.
Les teaches that the old nature declares war on the new nature, and the new nature must declare war on the old nature, creating a constant battle. The battle lines are defined from the moment of salvation until death or the Rapture. The old Adam, or flesh, lusts against the Spirit, and the Holy Spirit wars against the flesh. These two forces within every believer are contrary and at total odds; they cannot agree on anything because the new nature has new values aligned with God's righteousness, holiness, and laws, while the old nature, whose god is Satan, is bent in rebellion and unbelief. Thus they war constantly, so you cannot do the things you would.