“Things on a very small scale [like electrons] behave like nothing that you have any direct experience about. They do not behave like waves, they do not behave like particles, they do not behave like clouds, or billiard balls, or weights on springs, or like anything that you have ever seen.”
Richard Feynman
Book: What is a Thing?. Some pages about what is a thing and why things are important. A PDF file, 5mb
Probably in early history what defined a thing was the presence of the non-thing known as “air”—the tree is different from the mountain because there is air between them. It took thousands of years before science figured out that air was also a thing (even though the Greeks suggested it).
A thing can be material such as “car”, “table”, “mountain,” it may be more independent such as “body” or part of a larger thing like “hand,” it may be conceptual such as happiness, and a thing such as a smile or intelligence or beauty is in the eyes of the beholder and there are such things as integrity and honesty,
But while we share, or believe that we share, a common definiton of any specific thing, its more complicated. A thing such as a table—Whats the problem we all know what a table is— is a concept that we apply in a specific situation. If you ask me to go in the next room and get the book off the table and bring it back, if when I go in the next room the “table” might be the strangest looking table I ever sdaw, but still I will see it as a table. Perhaps I cannot even call it a table because of what it looks like, but only because of its function (a rose is a rose...).
While culture teaches us a common language, each of our experiences are unique and the meaning of the language may differ from person to person. And this meaning is inside of us, not apparent to others except if we express it, and someone hears it.. We may express it by words and again these are abstractions and sometimes misleading. Later when behaviours occur people find that they did not hold the same meaning for the “thing” resulting in an argument, court of law, a killing or a loss of friendship.
I discuss this in the “What is a Thing” book (available as a pdf download) which is more fun.
This is a collecton of posters where each of the pictures share something in common—they are same things. At the same time on any poster you can see how different each thing is from the other.