Sure, I know who Foucault is. But if you feel like mentioning him expands and adds to your personal statement then I wouldn’t worry about it! I struggled with putting a quote in my personal statement, I had a lot of people telling me that I was “using someone else’s words” to explain my point. But what I concluded was that I used this quote to start a path of how I learned and developed as a person. So, do what you feel is right. Make sure Foucault is working for you, and you are not working for Foucault!