That's exactly the point. A hertz is abstract, a dollar is not. A gold coin wasn't. Just like an apple is not abstract, money isn't also. (Unless you're talkin

That's exactly the point. A hertz is abstract, a dollar is not. A gold coin wasn't. Just like an apple is not abstract, money isn't also. (Unless you're talking about the general concept of "money", which is of course abstract, but the general concept of "apple" is abstract also.)