||Experimental evidence about the relationship between outdoor lighting and crime was examined in Part 1 of this work. Although the presence of light tends to allay the fear of crime at night, the balance of evidence from relatively short-term field studies is that increased lighting is ineffective for preventing or deterring actual crime. In this second part, available evidence indicates that darkness inhibits crime, and that crime is more encouraged than deterred by outdoor lighting. A new hypothesis is developed accordingly. Additional quantitative evidence supports the hypothesis. Excessive outdoor lighting appears to facilitate some of the social factors that lead to crime. The proliferation of artificial outdoor lighting has been fostered with little regard for the environmental consequences of wasteful practice. Widely observed exponential increases in artificial skyglow indicate that the growth of outdoor lighting is unsustainable. The natural spectacle of the night sky has already been obliterated for much of the population of the developed world. Copious artificial light has transformed civilisation, but increasing knowledge of its adverse environmental, biological and cultural effects now justifies large overall reductions in outdoor ambient light at night as well as in its waste component. âGoodâ lighting has to be redefined. Moderation of outdoor ambient light levels may reduce crime in due course, as well as limiting the adverse environmental effects. Lighting controls might provide a means of limiting urbanisation and urban sprawl. National crime prevention policies, laws, lighting standards, architectural use of light and urban planning practice appear in need of fundamental changes.