The Harsh Reality: They Do Exist
Before I met my roommate, I thought that I was one of the most intelligent people that I've ever met, pretentious, I know, but just being honest. When the material was upper-level undergrad or graduate level, I studied, but even at a top tier university, I got amazing grades with much less effort than most of my peers, which was convenient but in an odd way depressing and isolating; however, my grades dramatically changed after a lot of personal losses (this is relevant, see below).
I'm sure a lot of us are in awe of well renowned professors--if you're an academic, they're like rock stars, at least to me they are. I've always looked up to these people, they make me feel like there's a place for me in this world. Anyway, as a result of being extraordinarily depressed, I lost almost all of my confidence. Unfortunately for me, this was when I met my (now) roommate, which made me feel so much worse.
There are people who say that they don't study when they really do. There are people who appear to be really smart when they're really not. There's a major difference between knowing a lot of facts and actually being intelligent. My roommate is quite literally the most brilliant person I've ever met, including several Nobel laureates. After living with him, I discovered that he actually doesn't study, at least not like most people do. He can read something once, at a ridiculously fast speed--quite literally he can read a full textbook page in under 20 seconds and comprehend everything. This is not limited to any particular domain. There are countless times that I have gone to him with high level mathematics problems from disciplines that he's not too familiar with, and he's able to not only understand everything almost immediately, but he can synthesize beautiful solutions and explain the concepts to me better than my professors who've been in the field for years. I know it sounds unbelievable, but I assure you that it's true.
My roommate was a major stumbling block for me. After meeting him, I began to doubt my intelligence even more. If people like him exist, what the hell am I going to do? How could I possibly compete with him? I went to speak with a few of my professors to essentially ask them if they were like my roommate. If they all were, then I knew that I had no place in the academia. Fortunately, out of all of the professors that I talked to, every single one of them said that they struggled a lot. While some of them knew one or two people like my roommate, they reassured me that not only did they put a ton of work in and struggle, but they also doubted themselves all the time, and most still do.
I guess what I am saying is that sometimes it can make sense to feel like an imposter. Some people are just geniuses, and I do not use that term lightly. In the end, 99% of the best of the best of the best still struggle a lot. It's okay to struggle, it's good. It means that you're learning. For what it's worth, if you're accepted into a PhD program or lab or what have you, the admissions committee/PI made a conscious decision to say that they believe that you are good enough. I don't care if you think that you got in because you knew someone, and that person recommended you. (A) that happens all the time, and (B), they actually went out of their way to recommend you. They put their reputation on the line for you. They wouldn't do that unless they believed in you--these are really intelligent people, you didn't trick them. Finally, for the people who only think that they got to where they are because of hard work and not natural intelligence, I say to you (A) that's probably not true (smart people tend to think that because they struggle with stuff and finally understand it, that everyone can and that's patently false) and (B) you're more likely to be successful than someone smarter who doesn't put in as much work. Sorry for the really long answer, but I hope it helps someone. It made me feel better just writing it. Cheers!
One last thing, the more one travels down the rabbit hole, the more one realizes just how little they know. This can lead people to question their intelligence. It's pretty ironic, you're becoming more informed and because of it you feel less informed. In this case, you just need to take a step back and realize that true mastery is impossible. It should be a good feeling to learn that which one did not know before. It's doesn't mean that you're stupid, it means you're getting smarter. If you think that you know everything or even can know everything, then perhaps you are not that intelligent.