a sua propria existencia sob todas as condicoes possiveis.Duns Escoto, e depois Descartes, ligou o ser necessario a logica: um ser necessario e aquele cuja inexistencia seria auto-contraditoria. Os feijoes reais nao existem e auto-contraditoria mas apenas trivialmente porque a existencia foi inserida na definicao do sujeito. Isto nao faz dos feijoes feijoes necessarios. Se a existencia nao for inserida na definicao do termo sujeito, e duvidoso que qualquer negacao de existencia seja auto-contraditoria. A melhor discussao da nocao de ser necessario e a de Alvin Plantinga (1974, 1975).Alasdair MacIntyre e Keith CampbellBibliografia historicaFontes primarias * Baumgarten, Alexander Gottlieb. Metaphysica. Halle, 1740. * Clauberg, Johannes. Opera Omnia, edited by J. T. Schalbruch. 2 vols., 281. Amsterdam, 1691. * Duhamel, Jean-Baptiste. De Consensu Veteris et Novae Philosophiae. Paris, 1663. * Duns Scotus, John. Opera Omnia. 12 vols. Paris, 1891-1895. Vol. III, Quaestiones Subtillissimae Super Libros Metaphysicorum Aristotelis. * Heidegger, Martin. Being and Time. Trad. John Macquarrie e Edward Robinson. New York: Harper, 1962. * Heidegger, Martin. Existence and Being. Trad. D. Scott, R. Hall, e A. Crick. Chicago: Regnery, 1949. * Kant, Immanuel. Critique of Pure Reason. Trad. Norman Kemp Smith. London: Macmillan, 1929. * Quine,Willard Van Orman. From a Logical Point of View. Cambridge, MA: Harvard University Press, 1953. * Wolff, Christian. Philosophia Prima Sive Ontologia. Frankfurt and Leipzig, 1729. * Wolff, Christian. Philosophia Rationalis, Sive Logica Methodo Scientifica Pertractata et ad Usum Scientiarum Atque Vitae Aptata. Frankfurt and Leipzig, 1728.Fontes secundarias * Bochenski, I. M. PhilosophyAn Introduction. Dordrecht, Netherlands, 1962. * Drennen, D. A., ed. Modern Introduction to Metaphysics. New York: Free Press of Glencoe, 1962. * Ferrater Mora, Jose. On the Early History of Ontology. Philosophy and Phenomenological Research 24 (1963): 36-47. * Geach, P. T., A. J. Ayer, and W. V. Quine. Symposium: On What There Is. PAS, Supp., 25 (1951): 125-160. * Gilson, Etienne. Being and Some Philosophers. Toronto: Pontifical Institute of Mediaeval Studies, 1949. * Martin, Gottfried. Immanuel Kant: Ontologie und Wissenschaftstheorie. Cologne: University of Cologne, 1951. Trad. P. G. Lucas, Kant Metaphysics and Theory of Science. Manchester, U.K., 1955. * Marx,Werner. Heidegger und die Tradition. Stuttgart: W. Kohlhammer, 1961. * Owens, Joseph. The Doctrine of Being in the Aristotelian Metaphysics. Toronto: Pontifical Institute of Mediaeval Studies, 1951.Bibliografia contemporanea * Adams, R. M. Primitive Thisness and Primitive Identity. The Journal of Philosophy 76 (1979): 5-26. * Alexander, Samuel. Space, Time, and Deity: The Gifford Lectures at Glasgow. 2 vols. London: Macmillan, 1920. * Armstrong, D. M. A Combinatorial Theory of Possibility. Cambridge, U.K.: Cambridge University Press, 1989. * Armstrong, D. M. Universals and Scientific Realism. 2 vols. Cambridge, U.K.: Cambridge University Press, 1978. * Armstrong, D. M. A World of States of Affairs. Cambridge, U.K.: Cambridge University Press, 1997. * Campbell, Keith. Abstract Particulars. Oxford: Blackwell, 1990. * Ellis, Brian. Scientific Essentialism. Cambridge, U.K.: Cambridge University Press, 2001. * Feibleman, James K. Ontology. Baltimore: Johns Hopkins Press, 1951. * Field, Hartry. Realism, Mathematics and Modality. Oxford: Blackwell, 1989. * Field, Hartry. Science without Numbers: A Defence of Nominalism. Oxford: Blackwell, 1980. * Forbes, Graeme. The Metaphysics of