Heinz von Foerster
was an Austrian physicist, systems theorist, radical constructivist, and philosopher. He was a polymath, traversing different disciplines seamlessly and effortlessly.
Right after I had finished my Abitur (the German A-levels), I spent a fair bit of time branching out, reading up on topics I didn't have the time or energy to read up on when I was a high-school student. It was a wonderful time that brought me in touch with a lot of different perspectives and ideas, one of them being Heinz von Foerster's way of thinking.
To me, his work is characterized by a deep sense of responsibility and playfulness. His research had brought him to the conclusion, that perception is not independent of us acting in the world: in order to see, we need to interact with the world. Our actions affect our way to see the world, which in turn affects our actions. Perception and action are thus intricately linked, something that is scientifically shown via Molyneux's problem (see the box below).