Quan hệ giữa người với người ngày càng mang tính nhân đạo cao hơn. Ngay trong xã hội nguyên thuỷ đã có những hình thức đơn giản của sự tương trợ và không còn tục ăn thịt người. Với sự xuất hiện của liên minh bộ lạc và nhà nước, tục báo thù của thị tộc dần dần mất đi. | 244 Bibliography Brown Lester R. and Kane Hal Full House Reassessing the Earth s Population Carrying Capacity New York Norton 1994 . Burgess J. A. and Tawia S. A. When Did You First Begin to Feel It Locating the Beginnings of Human Consciousness Bioethics 10 No. 2 Jan. 1996 1-26. Burton Keith A Chronicle Dax s Case As It Happened in John D. Arras and Bonnie Steinbock eds. Ethical Issues in Modern Medicine Mountain View Calif. Mayfield 1989 195-9. Callicott J. Baird Animal Liberation A Triangular Affair In Defense of the Land Ethic Essays in Environmental Philosophy Albany NY State University of New York Press 1989 . ---- The Case Against Moral Pluralism Environmental Ethics 12 No. 2 Summer 1990 99-124. ----Earth s Insights A Survey of Ecological Ethics from the Mediterranean Basin to the Australian Outback Berkeley and Los Angeles University of California Press 1994 . ----In Defense of the Land Ethic Essays in Environmental Philosophy Albany NY State University of New York Press 1989 . ---- On the Intrinsic Value of Nonhuman Species in Bryan G. Norton ed. The Preservation of Species Princeton NJ Princeton University Press 1988 138-72. ---- Traditional American Indian and Western European Attitudes Towards Nature An Overview Environmental Ethics 4 1982 293-318. Carnap Rudolf Psychology in Physical Language in A. J. Ayer ed. Logical Positivism New York Free Press 1969 . Carruthers Peter The Animals Issue Moral Theory in Practice Cambridge Cambridge University Press 1992 . Cavalieri Paola and Singer Peter eds. The Great Ape Project Beyond Human Equality New York St. Martin s Press 1993 . Chasoff Ira J. The Prevalence of Illicit Drug Use during Pregnancy and Discrepancies in Reporting in Pinellas County Florida Aew England Journal of Medicine 344 1990 1202. Cheney Jim Callicott s Metaphysics of Morals Environmental Ethics 13 No. 4 Winter 1991 311-26. Churchland Paul M. Folk Psychology and the Explanation of Human Behavior in John D. Greenwood ed. The Future of Folk .