What is “the definition of a professional career”?

I happened to come across this post from 2015 where I discussed a remark from a political journalist who advocated “some measure of accountability . . . which allows both that very bad teachers be fired and that very good ones can obtain greater pay and recognition. That’s the definition of a professional career track . . .” What interested me there was not the question of how easy it should be to promote or fire teachers, but rather the idea that the risk of being fired is part of “the definition of a professional career track.” OK, I’m not trying to take him literally. If you look up “professional” in the dictionary it says, “engaged in a profession that requires academic learning as preparation,” and if you look up “profession,” you get “a calling requiring specialized knowledge and often long and intensive academic preparation.” Obviously he didn’t literally mean that being fired is part of the definition, more that it’s a core or essential part of what being a professional is. It…