• this is interesting when compared to the concept that thinking requires some kind of externalization - Situated Cognition - the same way we can externalize our thinking to some medium (like Thinking by Writing), we have to have a substrate to think about, to notice the patterns of thinking itself
• one realisation of this is Metacognition when Debugging - thinking about the possible problem in the algorithm allow us to think about our thinking process
• some of these ideas might originate in David Hume (mind doesn't exist without perceptions), and Immanuel Kant (on impossibility of extracting humans from thinking about human knowledge)

You can't think about thinking without thinking about thinking about something

— Seymour Papert

Seymour Papert used to say "You can't think about thinking without thinking about thinking about something". In other words, it will really help to have important issues and ideas, and things to learn about that require much better thinking. Then, the many things that are known about thinking, how poorly we are generally at it, and what we've learned about doing it better, can be brought to bear.

— Alan Kay - https://www.quora.com/How-do-I-learn-to-think-better/answer/Alan-Kay-11

you can’t think about tools for thought without thinking about thinking and thinking about who gets to think about thinking

— May-Li Khoe - https://twitter.com/mayli/status/1387856536832147457