[1] In the 19th century, mathematician and philosopher Gottlob Frege argued against it, and contrasted it with mediated reference theory.
"[3] Direct reference theory is a position typically associated with logical positivism[3] and analytical philosophy.
Logical positivist philosophers in particular have significantly devoted their efforts in countering positions of the like of Wittgenstein's, and they aim at creating a "perfectly descriptive language" purified from ambiguities and confusions.
[3] The philosopher John Stuart Mill was one of the earliest modern advocates of a direct reference theory beginning in 1843.
Overall, Mill's argument is quite similar to the description theory of reference, with the exception of his view on proper names.
[7] Saul Kripke defended direct reference theory when applied to proper names.
Then (2), the experimenter must imagine the possible states of affairs that reality could have been - where Bush was not president, or went into a different career, was never born at all, etc.