According to Mandeville and Adam Smith,″private vices″and″personal benefits″bring ″public benefits″when it is″lopped by justice″or under the guidance of″invisible hand,″and form win-win situation of human beings and a rich harmonious society ;the economics also violates its ″no free lunch″motto,and suggests that″external diseconomy″is inessential and eliminable .In the light of the theory of″subversive″ecology,Hardin provides an important but incomplete criticism-externality is essential in″the game of win-or-lose,″and becomes eliminable when ″freedom of use″and″private property right″is regarded to be the cause and countermeasure of ″tragedy of the commons .″ Nature and anti-nature are two contrary evolutions,while there are two corresponding modes,free lunch and paid lunch ;natural evolution of earth system,″degeneration of the system in the earth-evolution of the earth surface system″(Ⅰ),″degeneration of natural system-evolution of life system″(Ⅱ),is an entropic process that provides life with″free lunch .″ In the aspect of externality judgment,biosphere is a reference system ;an essential judgment is ecological purpose,that is,to maintain biosphere diversity,harmony,stability and continuity . By playing ecological role,undertaking ecological obligation,complying with the order of nature,minimizing resource allocation and chasing ecological purpose,living beings become one″node″of biosphere″seamless web .″Living beings'low-level externality within the biosphere is dissolved at the high level and biosphere level ;closed circulation of materials prevents wastes forming in the biosphere,while water and atmospheric circulations spread waste heat to outer space .Maximized resource allocation,a must for″human beings″becoming human beings and social development,leads to destruction of the order of nature and fragmentation of biosphere ;human beings no longer play ecological role and undertake ecological obligation,so″ecological purpose″and ″ecologicalobligations right″are lost-as a result,human beings become inorganic members of biosphere,and are no longer qualified to have″free lunch″and they are deeply stamped with the mark of externality . The nature has no obligation to eliminate wastes and waste heat produced by human beings ; and it doesn't have this capability due to the restraint from the″adaptation-coordination″of its mechanism and the functional coupling of national circulation .With the existence of″redundancy function,″the nature can bear a few populations that″force their way into the nature ;″exponential growth of wastes and waste heat in human society leads to destruction of natural circulation mechanism,functional declination and serious social-natural crisis at present ; to reduce population-economy size substantially and implement″food-oil″strategy is the fundamental and the only way to deal with external″size crisis .″″Know yourself″is an eternal topic engraved by ancient Greeks on stone corridor at the Temple of Delphi .Lagging development of contemporary environmental ethics is caused by a fundamental misunderstanding-human beings are regarded to be one″node″of biosphere ″seamless web″(deep ecology) .Win-win between human beings and the nature and″inverted U-shaped curve relation between economy and environment″are argued repeatedly and circularly . Against this background,this paper discusses human beings' essentially external attempts .As a critical thinking and inferential paper,argumentation seems a little insufficient here .