Vladimir Karpovich Dmitriev writing in 1898, Ladislaus von Bortkiewicz writing in 1906–1907 and subsequent critics have alleged that Karl Marx's value theory and law of the tendency of the rate of profit to fall are internally inconsistent. In other words, the critics allege that Marx drew conclusions that actually do not follow from his theoretical premises. Once those errors are corrected, Marx's conclusion that aggregate price and profit are determined by—and equal to—aggregate value and surplus value no longer holds true. This result calls into question his theory that the exploitation of workers is the sole source of profit.