Step 1. Let's define "commerce." You know, people buying and selling things, making favorable trades and such. Let's agree that we recognize that this is a thing that has happened for a long time and is likely to happen for a long time. You might say it's "good," or you might just sort of accept it -- and perhaps if you're not willing to accept it, you at least understand that you have a ton of work ahead of you if you're going to get rid of it.
Now, how is "capitalism" different from the above? And again, note that even if you have an elegant and clear answer, others don't. I'm literally asking this question because I don't think we've come remotely close to STARTING a good definition here, collectively.