a person who thinks all the time has nothing to think about except thoughts

Ludvig! You are largely tight to right on this matter -- for thinking is individual only, and a society does not think thoughts in the immediate sense! But in the long term sense it does! Because we do indeed think jointly! And how is that? HERE, here in these words, you the reader have my thoughts too! And my thoughts include the words, the alphabets, the tools and means of conveying ideas such as paper, such as computers, screens, keyboards, etc. -- all of which include indirectly the thougts of others and even do so directly. For we do not share thoughts but what have understandable, society defined words and meanings, and likewise too with most understandings we take away from viewing images and photos. A person in a culture frames nearly all thoughts from the media developed by many humans in societies from long ago, and in the now.