However, while realist sociologists argue that criminology should treat crime as a real problem they have very different ideas about that problem. Left realists, like Young, have their roots in Marxism and radical criminology yet criticise Marxists for their "left idealism". They identify a number of causes of crime, including subcultures and relative deprivation. They favour police reform to create a more consensual police force that would better represent the population it polices. Tony Blair, when he became Labour leader in 1994, was greatly influenced by left realist ideas and his slogan "tough on crime, tough on the causes of crime" is sometimes seen as an expression of the left realist position.