I just started to read this book on category theory.
How is this example below a category?
I have difficulty imagining what this construct really is.
Could someone please illuminate me ?
I have a physics background, I am not a mathematician.
Perhaps with some very simple example or analogy that is understandable for a physicist's mind.
Thanks for reading.
Does this example make sense at all ?
What confuses me is that for a given object $A$, $i=|A|$ is fixed, so is $j=|B|$, so the location of a natural number in the matrix $F$ is determined by the size of $A$ and $B$. So the arrow from $A$ to $B$ is a number in a matrix and not the matrix itself !
EDIT 3: Many thanks for the answers ! I think I get it now.
As a reminder a category is defined as:
I just bought the latest eBook version where this mistake has been corrected: