natural.md

@@ -17,6 +17,11 @@ fib n = fib (n-1) + fib (n-2)
 
 But what is the value of **fib (-3)**?  A runtime stack overflow!  Much better to catch this error at compile time.
 
+## Comment
+
+
+If we do add them, then (a) they should probably be arbitrary in size; and (b) function definitions like fib should \*not\* be overloaded on Num, but should be monomorphic in Nat.
+
 ## Proposal