Dear Mr. C:
You wrote:
I have read the article you already have posted but my question is this: When someone asks me how I am doing, I will usually say, “I’m doing well.” My friend corrected me and said, “You can’t do well, you ARE well or are DOING good.” That sounds incorrect to me. Is he right?
It depends on what you mean. “Well” is commonly an adverb. Adverbs do answer the question “How?” or “In what manner?” If you are in good health, you would normally say, “I am doing well.” “Well” modifies the verb “am doing” and tells us how you are doing. Your response for that question is fine.
However, your friend may be thinking of another context. While “good” is normally an adjective, it can be a noun as in “the greater good.” When you say “I am doing good,” “good” is the direct object of “am doing” and tells what you are doing. It does come across as immodest, but if you felt you had been involved in a meritorious activity, you could say “I am doing good,” i.e. “I have been doing a good deed.” We are more likely to say that about others; for example, the Bible in Acts 10:38 has Peter saying that Jesus “went about doing good.”
“Well” can also be an adjective meaning “in good health.” If you were to say, “I am well,” meaning that you were in good health, that is acceptable. This may be what your friend was thinking of.
I hope this helps.