Yes, for common people, there is really no need to spend much time on thinking about some unrealistic philosophical questions. Are you the same person as who you were yesterday? Is the world your own world or is it shared by all other people? Well, getting the answer to these questions won’t make a single bit of difference in your daily life, not to mention that there probably won’t be an answer at all.

But some people do get fascinated in these questions.

Imagine you are using a computer and you want to calculate 13579 times 24680. You just need to know how to use the mouse, keyboard, and the Windows(or Mac) calculator application. You don’t bother to know how computers work internally. Why? Because you are busy. You have to work, you have to earn money so you can pay your rent and buy some food and have a good life. Your time is scarce and precious. Not all of us are Prince William or the son of Bill Gates. Even if you were, you probably would rather spend your time playing golf in Hawaii than learning some computer geek shit. Hey, I’m not saying this is bad or this is wrong. I’m saying the exact opposite. This is a wise decision for most people, I’d say. You do what you need to do, live a good life, and that’s more than enough.

I think philosophy is all about questioning what you see on the surface and trying to figure out what is actually happening underneath. Think about a farmer who lived thousands of years ago. He saw the sun rising up from the east and going down to the west every day. He wouldn’t be able to tell that the earth is actually orbiting the sun. Even if somehow he had known that, it would’ve had nothing to do with his life. He would still starve to death if, for example, he had a poor harvest. But does it mean that knowing the earth orbits the sun is meaningless? I wouldn’t say that.

Imagine in an imaginary world, there was an Army General whose name was Alice. In her office, she had a radio on her desk. She loved it. Everyday she spent a lot of time listening to it. Somehow, what she didn’t know was, that every night after she left, her secretary would come into her office and replace the radio with a new one. We aren’t quite sure why her secretary did that, perhaps for security reason. The new radio looked exactly the same as the old one, and it was placed at the exact same place on the desk by the secretary. The secretary made sure nothing seemed to have changed. That means, if there’s a scratch on the old radio, the secretary made a copy of that scratch on the new one, too. We assume the secretary did everything perfectly. General Alice never found out her radio was replaced everyday. She naively believed that her radio had always been the same one straight from the beginning.

Everything had gone seamlessly well for quite a long time, until one day general Alice’s radio stopped working abruptly. Alice was sad. She called her secretary and asked for help. Her secretary then responded with a fairly reasonable answer, said, “No big deal, general. I’ll just bring you a new one.” However, general Alice was sentimental over her good old radio and wasn’t happy about this answer. She said angrily, “What are you talking about? I’ve been using this radio for years! It is special to me. You gotta repair this radio, not to bring me a new one!”

Well, general Alice didn’t know that her radio was entirely a new one everyday and hence felt so sad thinking that she could no longer use it. From the secretary’s perspective, however, her words were unreasonable, even ridiculous, because the radio was replaced each day anyway. Well, let’s finish the story here. It’s just a metaphor.

What I want to tell you is that we are actually like general Alice, and our lives are like the radio. Feel confused? No worries, I know it’s not an easy concept to understand immediately. I will write more articles in the future to help everybody understand. But for now, for people who desperately wants to know what life is all about philosophically, here it is. This is a problem of identity. You think you are always the same person, or the same mind, or the same soul (whatever you’d like to call it) as who you were before, just like general Alice thinks that her radio is always that same old radio. But in fact, It’s not. You’re not, either. You’re not who you were yesterday. You are not who you were an hour earlier. You are not even who you were a milli-second earlier. It’s just who you think you are, not who you actually are. You are no longer that old person yesterday, but a new person now.

I would say at every different time point, you are a completely different person. Your memory convinces you that you are always the same person as who you were before. That’s just a trick of the mind you get from your memories. It is an incorrect illusion. You’ve never doubted it before, but if you do, you will soon find out that it is incorrect. Remember in the story above, general Alice is oblivious to the fact that her radio has been replaced because the new one has the same scratches as the old one. This is the problem. She never thinks of the possibility that her secretary does that intentionally. People naturally won’t question what they see on the surface. You think you are still who you were previously because you have the memory of your past! Well, maybe I should say his/her past, since you two are not the same person. Although the story may not be a perfect analogy, the idea is the same. What appears on the surface isn’t necessarily how things work deep underneath.

The fact is, we are not the same person we were before. We change constantly and continuously. We change every hour, every second, every milli-second. The change may be tiny, may be unobserved, may be ignored, but it is a change. This is a very important concept. From this concept and moving on, we will come to see more interesting conclusions.

Professor Card wrote a recommendation letter for me in 2020. I really appreciate him doing that. When I heard he got the Nobel Prize, I felt happy for him. I sent an email to congratulate him. I was thinking that he must be bombarded with emails and calls at the time, and so probably wouldn’t be able to read my email. To my surprise, he replied in a short time, said he was glad to know his class is still useful to me in computer science.

I got to know Prof. Card in the spring semester of 2019, when I took his course Econ-142 Econometrics and Statistical Learning at Berkeley. I barely got enrolled in the class because it was very popular at the beginning of the semester. People were already saying he was gonna win the Nobel Prize at the time, though he ended up missing it that year. The class was more than full. Many students were sitting on the ground.

But only after two weeks, enrollment dropped sharply to just about 60%, because many people found it too difficult and they quitted. I was also seriously discouraged the first time I went to the lecture. The slides were full of complicated matrix-calculation. I thus planned to quit as well. Somehow, God has his plan. Another course I was on the waitlist of turned out to be unavailable at the end, which left me no choice but to take David’s course, for I had to get enough credits. This forced me to grind so hard to figure out what the heck was in the first few lectures. I didn’t put much effort into it earlier because I thought I was gonna drop it anyway.

Well, after spending hella time reading books and picking up the linear algebra stuff that I barely remembered, I gradually came to get the gist of it. Things are always like this: Once you’ve done it, you can do it thereafter. It somewhat surprised me how fast I changed from a student being stunned by the math to become someone who represented the highest math skill level in the class. For students who are considering taking Econ-142, I’d say, the first few weeks are going to be tough, but once you’ve made it there, it’s all plain ground up ahead.

So, unsurprisingly, I went on doing pretty well in the midterm exam, got the highest score in the class. After the midterm, David said to the class that our grades weren’t quite good except two students who were way above the others. I told my friend Cecil, who sat right next to me, that I was sure the two guys he referred to were us. I knew Cecil is smart. I proved to be right after marks were released. Then I went to see Prof. Card for the first time in his office hours, sort of wanting to show off and let him know me personally.

David is very chill. I started to visit his office frequently. Looking back from today, some questions I asked him were very basic, but he was always so kind and patient to answer me. I guess that’s one of the reasons why he is well respected.

I got an A+ for this course. That’s the only A+ I had at Berkeley. I could’ve had another one from STAT-150 Stochastic Processes, but I forgot to turn in homework too many times, gee. I asked Professor Card for a recommendation letter. He agreed and we had a short talk. I was a little worried when he asked me about my GPA in China. But here is what happened, when I was saying “I don’t have good GPA in China because the courses are”, he interrupted and said, “Because they are all stupid stuff?”

Yes, Sir! That’s what I’m talking about. It feels so good to have someone who understands you, especially if he is a Nobel-Prize winner.

Time flies. It’s been two years now since I left America. I miss those days. Lake Tahoe, San Francisco, Evans Hall, friends and professors. Time really flies. Professor Card, I don’t know if I’ll see you again. But if you were to read this post, I’d like to let you know: Thank you. Your class is awesome. You are the coolest professor I’ve ever known!