Hey you. Yes, you, the reader. You clicked on this article because you have some degree of impostor syndrome. That feeling where you think you've somehow faked expertise to get where you are in your career, or that everyone else knows more than you. That you're helplessly flailing and hope nobody will figure out that you're a fraud.
I have good news. No matter your skill level, no matter your position, you're not an impostor.
"Ipse se nihil scire id unum sciat."* - The Socratic Paradox
The Socratic Paradox is usually paraphrased as something along the lines of "all I know is that I know nothing". The more one learns about a subject, the more one learns just how much there is to learn. The simplest subjects have thousands of years of history behind them; the most complex ones require learning the summarized, accrued knowledge of thousands of years of expert study. There is not a single thing that you can learn fully and completely, even given a lifetime of devoted study. Someone will always know something that you don't know, because everyone has a different perspective.
You are where you are because you have learned a difficult skill -- how to program a computer. You may have more specialized knowledge in a particular area than some other programmer, you may know less than someone who has been programming for longer than you, but you absolutely know more than the average person. Don't get distressed because you aren't an expert in the en vogue framework or you haven't yet learned a functional programming language. Paradoxically, the fact that you're self-aware enough to have impostor syndrome in and of itself means that you shouldn't think of yourself as an impostor. You are aware of the limits of your knowledge. You know what you need to learn to stay competitive, or advance your career, or stay at the cutting edge of your particular niche.
The people who don't have impostor syndrome are the ones you want to avoid.