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In philosophy, four-dimensionalism (also known as the the doctrine of temporal parts and the theory that objects "perdure") is an ontological position that an object's persistence through time is like its extension through space and an object that exists in time has temporal parts in the various subregions of the total region of time it occupies.

Four-dimensionalism may refer to either eternalism or perdurantism. Eternalism is a philosophical approach to the ontological nature of time, according to which all points in time are equally "real", as opposed to the presentist idea that only the present is real. Perdurantism or perdurance theory is a philosophical theory of persistence and identity. according to which an individual has distinct temporal parts throughout its existence. Thus eternalism is a theory of time, while perdurantism is a theory about the identity of objects over time. Sider (1997) uses the term four-dimensionalism to refer to perdurantism. Eternalism and perdurantism tend to be discussed together because many philosophers argue for a combination of eternalism and perdurantism, considering both as better theories than their counterparts, presentism and endurantism, respectively. It may be argued that the acceptance of perdurantism and rejection of eternalism would would be incoherent.

Contemporary four-dimensionalists include, according to Sider (1997), Armstrong (1980), Hughes (1986) , Heller (1984, 1990,1992,1993) and Lewis (1983, 1986).

Background

As four-dimensionalism (understood as either eternalism or perdurantism) is a metaphysical theory, it is necessary to say something here about the aim of metaphysics. Like science, the aim of metaphysics is to understand as much as possible in terms of as little as possible. In other words, the aim is to reduce the number of fundamentals to a minimum, and understand everything else as if constructed in some simple way out of those fundamentals. If a theory of x maintains that x is a fundamental element of reality, then this is expressed in this article by saying that the theory is a metaphysical "dead end" theory (of x). The background assumption is that reduction of fundamentals will lead to a true picture of reality. If we can understand space in terms of fundamentals x, y, z, etc., then all the better if we can also understand time in terms of x, y, z, etc. Eternalism attempts to do just that. Time is understood as the fourth dimension, equivalent to the three dimensions of space. What we lose from this theory is any special status for the present, however special it might seem...

Temporal parts

Temporal parts is a concept used in contemporary metaphysics in the debate over the persistence of material objects. Objects typically have parts that exist in space—a human body, for example, has spatial parts like hands, feet, and legs.

Presentism vs. eternalism

Presentism is an ontological viewpoint which attempts to account for how consciousness functions in relation to time. Presentism asserts that only the present exists. The past and the future, therefore, are seen as non-existent. To a presentist, the memory accounts for the collection of events that have already occurred. Similarly, the future is conceptualized as being a mental construct. Therefore, presentism is attempting to demonstrate that the total sum of the actual world occupies the present moment.

Consequently, eternalism is the ontological view which postulates that past, present and future all equally exist. While the presentist asserts that the past and future are only logical constructs, the eternalist believes that time exists as an objective manifestation. Eternalism is the basic construct behind four-dimensionalism, as it accounts for the reality of past and future rather than proposing that all events occupy the present.

A-series and B-series

J.M.E. McTaggart in The Unreality of Time, identified two descriptions of time, which he called the A-series and the B-series. The A-series identifies positions in time as past, present, or future; the B-series, as earlier than or later than some time position.

Comparisons to three-dimensionalism

The three dimensionalist view imagines time as being a unique dimension, not analogous to the three spatial dimensions: length, width and height. Whereas the four dimensionalist proposes that objects are extended across time, the three dimensionalist adheres to the belief that all objects are wholly present at any moment at which they exist. While the three dimensionalist believes that objects can be differentiated based on their spatial dimensions, the same does not apply to time. Rather, the existence of temporal parts is a linguistic construct. For example, the person described by the phrase “Descartes in 1635” is objectively the same as the person described as “Descartes in 1620.” Temporal parts are not existent for the three dimensionalist. Therefore, change does not need to be accounted for. Accordingly, the only relation between these objects is that of identity. This helps to account for the paradox of change.

The four-dimensionalist view, by contrast, asserts that all objects occupying different time frames are inherently different versions of the same object. In order to account for these different versions, the notion of temporal parts is introduced. Differences among temporal parts are how a four-dimensionalist accounts for change. Thus, the temporal part described by the phrase “Descartes in 1635” is different from the temporal part described by the phrase “Descartes in 1620.” When combined, these parts form a spacetime “worm.”

See also

• Rietdijk–Putnam argument for an argument advocating this position.

References

1. ^ Sider, Theodore (1997). "Four-Dimensionalism" (PDF). The Philosophical Review. 106 (2). Duke University Press: 197–231. JSTOR 2998357. {{cite journal}}: Unknown parameter |month= ignored (help)
2. Kuipers, Theo A.F. (2007). General Philosophy of Science: Focal Issues. North Holland. p. 326. ISBN 978-0444515483.
3. Hawley, Katherine (2010). "Temporal Parts". In Edward N. Zalta (ed.). The Stanford Encyclopedia of Philosophy (Winter 2010 ed.).
4. ^ "Time". Stanford Encyclopedia of Philosophy. 2002-11-25. Retrieved 2008-12-15.

• Armstrong, David M. (1980). “Identity Through Time.” In Peter van Inwagen (ed.), Time and Cause, 67-68 Dordrecht: D. Reidel.
• Hughes, C. (1986). “Is a Thing Just the Sum of Its Parts?” Proceedings of the Aristotelian Society 85: 213-33.
• Heller, Mark (1984). “Temporal Parts of Four Dimensional Objects.” Philo-

sophical Studies 46: 323-34. Reprinted in Rea 1997: 12.-330.

• Heller, Mark (1990). The Ontology of Physical Objects: Four-dimensional Hunks of Matter.

Cambridge: Cambridge University Press.

• Heller, Mark (1992). “Things Change.” Philosophy and Phenomenological Research 52: 695-304
• Heller, Mark (1993). “Varieties of Four Dimensionalism.” Australasian Journal of Philosophy 71: 47-59.
• Lewis, David (1983). “Survival and Identity.” In Philosophical Papers, Volume 1, 55-7. Oxford: Oxford University Press. With postscripts. Originally published in Amelie O. Rorty, ed., The Identities of Persons (Berkeley: University of California Press, 1976), 17-40.
• Lewis, David (1986a). On the Plurality of Worlds. Oxford: Basil Blackwell.
• Lewis, David (1986b). Philosophical Papers, Volume 2. Oxford: Oxford University Press.
• McTaggart John Ellis (1908). "The Unreality of time" in Mind: A Quarterly Review of Psychology and Philosophy 17 (1908): 456-473. <http://en.wikisource.org/The_Unreality_of_Time>

• Lewis, D. 1976: Survival and identity. Pp. 17-40 in Rorty, A.O. (ed.) The identities of persons. Berkeley: University of California Press. Google books
• Markosian, N. 2004: A defense of presentism. Pp. 47-82 in Zimmerman, D.W. (ed.) Oxford Studies in Metaphysics, Volume 1. Oxford: Oxford University Press. Google books
• Muis, R. 2005: Four-dimensionalism: an ontology of persistence and time. By Theodore Sider. Ars Disputandi, 5 ISSN: 1566-5399 PDF
• Robinson, D. 1985: Can amoebae divide without multiplying? Australasian journal of philosophy, 63(3): 299–319. doi:10.1080/00048408512341901

External links

• Rea, M. C., "Four Dimensionalism" in The Oxford Handbook for Metaphysics. Oxford Univ. Press. Describes presentism and four-dimensionalism.
• "Time" in the Internet Encyclopedia of Philosophy

• Philosophy of time
• Philosophy of physics
• Spacetime