The old man defined. Paul does not mean here what is often called ‘the old nature’. What he means by the old man is humanity in Adam. We can perhaps see its meaning in connection to the way Paul has already used the illustration of a man in verse 13, when he said that the glorified church would be a perfect man. When Paul speaks about the old man, he means sinful humanity.
The old man described. Paul describes sinful humanity as ‘corrupt through deceitful desires’. The word ‘corrupt’ means rotten, a vivid picture of the spiritual death that sin has brought into the human race. This degradation is brought about by desires marked by illusions. Their desires were based on what was false, with no satisfaction or fulfilment.
The old man discarded. Paul reminds the Ephesians that their past behaviour had been the same as everyone else in the sinful humanity. But that humanity has to be discarded, and its removal occurs in the three stages. When Paul writes to the Romans about the old man (6:6), he tells them that they have already put it off, which occurred when they were taken out of the old humanity and were united to Christ at conversion. In the future, they will lose all trace of the old humanity when they are made perfect in holiness. But in the present, because we are still sinful, we have to be careful that we do not live like the world, the old humanity.
Paul here is not speaking specifically about an inward battle. His illustration of putting off clothes indicates that it is visible, an outward thing, and indeed he goes on to give four examples: don’t tell lies, don’t retain anger, don’t steal, don’t have unhelpful speech.
These four features were and are seen in the old humanity. We are to put them off, but how. Paul gives the answer: by the renewing of our minds, in other words by thinking differently from fallen humanity. Initially, this renewing occurs at conversion, but it continues throughout one’s Christian life.