It’s occurred to me that several people with whom I interact have a knowledge of their vocation that seems to me, observing from the outside, as deep and complex as my own acquaintance with my profession. Ergo, the OP.
Does a codified ethical standard make the difference? If not, what does?
Traditionally, professionals were members of the “learned professions”, like medicine, law, accountancy, architecture, and engineering. These were usually state-regulated professions with licensing based on education, character and an exam or exams. Folks like executives, bankers and stockbrokers were considered businesspeople, not professionals.
However, more recently, the term professional has come to encompass a broad range of people who are not in formal professions, but are educated, highly compensated and do similar work. Perhaps related to this trend is the rise of the MBA degree, which is not entirely unlike the advanced educational training required in some professions.
Historically a “professional” went through more-or-less standardized training at a post-secondary school, was taught by a faculty even more learned in the profession and had to pass a standardized test.
A “tradesman” (a better term would be “craftsman”) acquired knowledge through on-the-job training. Typically, a craftsman would become an apprentice to someone experienced, and train by doing. While the craftsman might obtain a guild certification (e.g., a journeyman or master plumber), it wasn’t any “legal” certification and didn’t necessarily depend on passing a standardized test.