… is from page 221 of Israel Kirzner’s 1992 collection, The Meaning of Market Process; specifically, it’s from Kirzner’s 1990 essay “Discovery, Private Property and the Theory of Justice in Capitalist Society” (original emphasis):
A discovered outcome is not a result already embedded , in embryonic form, in any bundle of resources. The outcome of an act of discovery is thus originated entirely by that act. A newly discovered island rich in natural resources has been created, for purposes of social science, in the act of its discovery…. [A]s far as directly concerns human decision making and economic values – and human ethical judgements – the island entered into existence at the moment of its discovery. Its discoverer was its creator, for all purposes of human concern.