This tenet of rational expectations theory can be most easily understood through a concrete example.
Mishkin, Frederic S. Financial Markets, Institutions and Money (1995)
We can point to the polls as a very concrete example any time we are trying to sell ourselves.
Times, Sunday Times (2016)
We also introduce a new concrete example of a totient.
Pentti Haukkanen 1996, 'Some characterizations of totients', International Journal of Mathematics and Mathematical Sciences