Building Objects in Time - Spatio-temporal Approaches - page 17

1.2.1. Objects' formalization in time: “endurant” and “perdurant” entities of
philosophers
The dichotomy that the philosophers introduce between the “endurantist” and
“perdurantist” conceptions constitutes an enlightening starting point. It consists of
two ways of apprehending the world, following the way entities' relationship to time
is conceptualized. These two designs are sometimes regarded as opposed in
philosophy, giving rise to debates (for example [LEW 88, MAC 02]), but they can
also be interpreted as complementary. From a thematic point of view, when there is
a need to understand the dynamics of the geographical space, it is indeed the
complementarity of these designs that is relevant. In such a spirit, Grenon and Smith
[GRE 04] proposed to distinguish between the following two types of entities 9
(Figure 1.4):
-The entities called snap ( also called “continuant” or “endurant” by
philosophers) are entities that have the capacity to persist in time (hence, the term
“endure”) and that we can observe at any moment of their existence 10 . Therefore,
they exist in their entirety at each moment, maintaining their identity. They have an
extent in space (in other words, they have “spatial parts”) and make up a whole,
observable at each moment. However, they do not have “temporal parts” [HAW 04].
Individuals, trees, rivers, cities and administrative units are entities of this type. An
individual being does not have “temporal parts”, and if he/she evolves over time, it
retains his/her identity (Wilson the child and Wilson the pensioner refer to a single
person) [LIV 09]. The same happens for a city: Lyon retains its identity even if the
city of the middle ages has little to do with the city of today. It exists and can be
observed, characterized, at any date of its existence, from Roman antiquity to
nowadays. Properties (such as age, surface area and density) are also considered as
“endurant” entities. These entities depend on the objects they are associated with
(the age of an individual, the length of a river, the number of inhabitants of an
administrative unit and the density of a city) and do not have an existence outside of
them in the case of an object approach. In a field approach, a cluster of points
verifying the same property, defines a spatial extent associated with this property
(for example, the set of points having the same altitude that allows identifying the
equilibrium line of glacier and following the evolution of a glacier in time).
9 Within the meaning of the definition given in section 1.1.1, i.e. the objects, properties,
relationships, events and processes identified to describe and represent an area of interest.
10 The categorization introduced in the first part about bona fide versus fiat entities, also
makes sense in this context. When reference is made to the ability of a bona fide entity to
persist in time , its existence refers to its physical presence whereas for a fiat object (i.e. a built
object), its existence concerns the time of the convention (for example, Yugoslavia) or of the
conception.