Final answer:
Karl Marx is a sociologist who believed that the history of society was a class struggle and that the underprivileged could only achieve equality through ongoing struggle.
Step-by-step explanation:
Karl Marx believed that the history of society was one of class struggle, a central tenet in his theory of social change. Marx posited that the only way for the underprivileged to eventually gain some measure of equality would be to continue to struggle against each other, highlighting the inevitable conflict between different social classes. This contrasts with Herbert Spencer's Social Darwinism, which suggested that aiding the poor was futile because they were deemed naturally unfit.