Is the last book you read a thing? If it was a paperback, you would probably answer "yes" If your reading it as an ebook, it might not be so clear. It wouldn't exist like paper does, it would just be a "thing" of information on a memory chip. What about if it was an audiobook?
What are things?
Birds are things. Bird's beaks are things. Molecules are things. Chairs are things, as are galaxies and atoms and waves. I could list of an infinite list of potential candidates for being a thing and you could say for each, "Yes" or "No".
Its a thing. Or Not. Sometimes.... you may pause...
What about the number seven? Is that a thing? Or the number 7.34243 Or the square root of minus one? Or the meaning of the word "ironic" or twentieth King of France. Are they things? Its not so clear.
What do dictionaries say? Things like:
"A thing is an entity, an idea, or a quality perceived, known, or thought to have its own existence."
This dictionary definition points us in the right direction but it doesn't really capture the features of things, nor does it explain the features of non things and, it doesn't explain or contain any information about why what it contain is the case. For example, why are ideas things? Are experiences ideas? Are numbers ideas?
We use things lots in our conceptual framework, but most people, including me, haven't a clear answer of what things are.
An Elemental Definition specifies all statements that are true of the thing defined.
An Elemental Definition of "a thing" will be true of all things and there will be no elements of the definition that any given thing does not posses. Each element is necesaary but not sufficient for "thingdom".
A thing is contingent; it can only be, if certain other things are.
A thing is divisible; it contains elements that exist independent of the thing.
A thing is elemental; it can be an element in another distinct thing.
A thing is interconnected; it can exist in relationships with other things, as will its parts.
A thing is a reference; it can be represented.
A thing is countable.
A thing is possible.
A thing is imperminent; it can either be or not be.
So what things are thing, on this definition. All objects we interact with in he physical world are clearly things. Bank accounts are things. The experience of a tea ceremony in a Japanese tea-house is a thing. The penumbras of shadows are things.