What does it mean to say that old Adam is crucified?
It means God has declared old Adam dead in His mind. When a person believes the Gospel, God saw them in Christ on the cross, so old Adam is reckoned crucified. This is a judicial declaration, though old Adam still remains an influence in the Christian life.
Les explains that Paul writes as the believer who has reckoned old Adam crucified and dead, yet old Adam is still left as an influence even in the Christian life. Though there are two ways of looking at this, the teaching maintains that old Adam is crucified and declared dead in the mind of God. The moment a person believes the Gospel, God saw them in the person of Christ on the cross. This is possible because God is omnipotent and omniscient, and with Him nothing is impossible. Every child of Adam is sold under the curse and under old Adam, but the believer reckons old Adam crucified because God saw them in Christ on the cross.