Cultural critic and author Derrick Jensen argues that modern civilization is directed towards the domination of the environment and humanity itself in an intrinsically harmful, unsustainable, and self-destructive fashion. Defending his definition both linguistically and historically, he defines civilization as "a culture... that both leads to and emerges from the growth of cities", with "cities" defined as "people living more or less permanently in one place in densities high enough to require the routine importation of food and other necessities of life". This need for civilizations to import ever more resources, he argues, stems from their over-exploitation and diminution of their own local resources. Therefore, civilizations inherently adopt imperialist and expansionist policies and, to maintain these, highly militarized, hierarchically structured, and coercion-based cultures and lifestyles.