What are the key distinctions between the old man and old nature?

This text is from a transcript of a talk by David Gooding, entitled ‘God’s Power for Salvation’ (2005).

To answer what the old man is, let's look at the way it is used in the Epistles. Ephesians 4, for instance:

That you put away, as concerning your former manner of life, the old man, which waxes corrupt after the lusts of deceit; and that you be renewed in the spirit of your mind, and put on the new man, which after God has been created in righteousness and holiness of truth. (Ephesians 4:22–24)

The old man is said here to be 'your former manner of life, the old man'. And that former manner of life goes on becoming more corrupt after the lusts of deceit. It is the way you behaved and were before you were converted to Christ. It was a way of life. It wasn't merely that you did all sorts of deeds; it was that your mindset, your motivation, was that of the old man. And therefore the whole setup that was you—not interested in God, basically hostile to God, moved by ambitions that were selfish, perhaps—developed a whole lifestyle, a mental attitude, a moral attitude. It is your attitude of mind, what you were as the kind of man you were before you got converted.

With Saul of Tarsus it was a highly religious man but it was a mindset and an ambition that was absolutely hostile to Christ. Though he didn't know it, he was quite independent of God, thinking to gain salvation by his own works, which is a form of independence of God that is obnoxious to him. And it came with all the pride and conceit, and then bigotry and persecution, that went with it. That was the old man. And you saw what change was made in Paul through the death of Christ at the cross.

Then of course, from the practical side, he had to put off this old man, because there is a new life in Christ—a new man: new principles, new motives, new attitudes. It is a life based in a fear and love of God, and Christ dwelling within. In other words, the old man is not a part of us—the bad part of us, so to speak. It is the person we were before we came to Christ. And we put on the new man, though in one sense we are a new man in Christ. We are like a child that was born a beggar and is taken into a royal family and is now to be treated as a prince. We'll have to learn to put off the old man and the things and habits that went with being a beggar: the deceit, and this kind of thing, and put on the new man that is consistent with his new father, so to speak.