The structural identity refers to the sum total of physical characteristics of the object, i.e. all properties that can be detected by our senses (sight, as well as hearing, taste, smell, and touch), and by physical and chemical research techniques. Several authors have attempted to systematise the physical structure of objects in which the changes after the completion of the artefact play a key-role.

Elaborating on artefacts, the structural identity concerns:

These physical properties can be grouped according to three principles: intention (intentional vs. non-intentional information), perception (appearance vs. substance) and development (factual vs. actual identity).

Intentional information refers to properties that are the result of the intentional intervention of the maker or user(s). Non-intentional information refers to all properties that are included in the object due to the material used, the technology applied, and the results of deterioration. Examples of primary non-intentional structural information are: the chemical composition, trace elements, diatoms in clay, air bubbles, fingerprints in ceramics, etc. This non-intentional information is increasingly important in relation to scientific research (determination of provenance, dating, technological analysis, authentication).

Blok suggests a further distinction as to intentional information by speaking about the personal and impersonal poles of artistic communication (Blok 1994). The choices of the medium and of the method of the artistic expression are as important as the choice of artistic language. The choice of a technique and certain materials says something about the attitude of the artist in relation to the way in which art functions (personal element). But usually the choice is partly a matter of routine. This can by described as impersonal because in general artists work with materials and techniques that they have not discovered themselves and which they cannot entirely adapt to their particular requirements.

As to perception distinction can be made between image (appearance) and substance (Brandi 1977). The substance is the carrier of the image, which is sometimes referred to as the 'aesthetic surface' or the 'perceptual object' (Sagoff 1978). Image relates to morphology (sight and touch) as well as to sound, smell and taste. There is of course a link between intentional information and image, but the perceived image of an object might result from other physical characteristics than the intentional information alone (see below), whereas the choice of materials might be based on their metaphysical connotations rather than their appearance.

As to development it should be noted that in general the object as it appears to us now is not identical with the object as it was intended by the maker and as it appeared to him/her. This distinction between the original appearance (as aspect of the 'factual identity) and the actual appearance (as aspect of the 'actual identity') has been described by Brandi as 'aesthetic and historical duality' (Brandi 1977). The aesthetic dimension is related to the original appearance, as intended by the maker, while the historical dimension is connected with the actual state of the object. Schliessl adopts a more neutral approach by distinguishing between 'Erstzustand' and 'Istzustand' (Schliessl 1988: 58) [note 1].

Factual identity presupposes the existence of a 'finished object'. It is not always easy to establish when an artefact completed its genesis. In many cases the factual identity of a given object is a hypothetical construct. It involves a decision of the maker. But how to deal with the situation when the maker is not satisfied afterwards and wants to make changes? Such problems arise in particular when the maker is also the user and improves or adapts the object during use. Other complications arise when an object is left unfinished, or finished by somebody else at a later date. As the factual identity is an important point of reference in conservation and restoration it is necessary to develop a more precise terminology. Actual identity refers to the object as it appears to us now, as sum total of the primary data and the effects of use, deterioration, etc. (secondary data).

The factors determining the information content of the actual identity are [note 2]:

1 natural causes
a natural disasters
b climate (humidity, temperature, light)
c destructive organisms
d inherent material weakness
2 human causes
a neglect
b (economic) exploitation
c incompetent treatment
d vandalism
e war
f repairs, restoration
g changes in taste and ideology
h changes in function

- Natural disasters include earthquakes, floods, volcanic eruptions, hurricanes, landslides, fires caused by lightning and so forth. Less drastic agents fall under the general heading of climate, such as humidity, temperature and light. There are a number of animals (especially insects) that feed on organic materials. Plants can be destructive too, especially those that live on (in) dead organic materials (such as fungi).
- Deterioration can literally be built into a work by its creator through the choice of inappropriate or inferior materials, and by bad workmanship.
- Neglect is generally a complex factor generated by several conditions. First, a great deal of cultural property requires constant maintenance and repair so that it can withstand normal weathering. Neglect occurs when the requisite maintenance procedures are not longer carried out. This may be caused by economic obsolescence of the object (see Chapter 16) or by changes in priority by the owner.
- Use (i.e. economic exploitation) changes objects. Use involves wear, continuing use asks for repairs or adaptation. Complete or partial destruction for economic gain also takes many forms.
- Incompetent maintenance (by using wrong materials or destructive techniques) damages the surface of objects. Incompetent treatment takes many forms, 'even' museums are not free from it.
- Wars can be as destructive as natural disasters. Bombing destroys houses, even complete cities, and all the objects assembled. Certain cultural property may even be destroyed on purpose as an attempt to exterminate the cultural identity.

Ideology is a broad term which encompasses all manners of religious beliefs, civic ideals and world views specific to cultures and social groups. Taste refers to preferences for certain cultural values especially in the field of aesthetics. Changes in taste and ideology involves the destruction or adaptation of artefacts.

Barton has given an interesting example how changes in taste and ideology affects the appearance of artefacts (Barton 1985). In the late 19th century a decorative fashion concerning the display of Maori wood sculpture began affecting museums throughout New Zealand. This fashion (possibly initiated by the Auckland Museum) was to paint carvings and other wooden structures red following the (wrong) assumption that genuine Maori sculpture should be red coloured. After the Auckland Museum started to remove this 19th century paint in the 1980s a second fashion affected the appearance of wooden objects: the radical removal of red paint. Similar treatment of sculpture is known from Western European museums. For example, due to natural causes the original polychromy of Greek architecture and sculpture has mostly disappeared. Although as early as 1750 Stuart and Revett found traces of polychromy on Greek temples, the (neo-)classicist ideal was dominated by the white marble which prompted restorers to remove all traces of paint.

During August and September 1566 calvinists destroyed sculptures, altars and other religious objects in roman-catholic churches throughout the Netherlands. A change of ideology (combined with political motives) brought about a mass destruction of cultural property. Lucas van Leyden's triptych 'The last judgement' (1526-1527) was saved by the Leyden municipality. As reference to ultimate justice the painting could easily be fitted in a new, secular context. The image of God Father, however, was not acceptable and was overpainted (Levy-van Halm 1991).

Especially during the 19th century architectural style became instrument of ideological propaganda. Baroque buildings and baroque additions to older buildings became 'victim' of a purist gothic revival. But in their turn, neogothic buildings and neogothic additions disappeared during restoration projects of the 1950s and 60s, due to a new purist movement. Secondary information may also reflect a shift in morality. During the 1940s Cardinal Pedro Segura y Saenz (1898-1957) commissioned to remove the 'private parts' of the roman statues of gods and emperors in the collection of the Archaeological Museum at Sevilla (Spain). The cut off parts are still preserved in a cardboard box, carefully labelled (Bosschart 1984). The history of art is full of examples of prudery which destroyed or mutilated classical statues and mythological paintings.

Changes in function may also influence the appearance of objects. In the first place this regards adaptations following new interpretations of the factual function. For example, in the cause of time the interiors of churches have changed following new views concerning the liturgical demands. Already a decade before the directives of the Second Vatican Council the changes in the Roman Catholic Church of the Netherlands lead to new liturgical arrangements of church interiors, where the altar was placed as centrally as possible: close to, or in the midst of, the faithful, on a low platform on which the priest could officiate facing the people (Peeters 1984). Old churches were adapted to this new view, often without respecting the old furniture and decorations and without putting the question whether the new liturgy needed adaptations within a church of historical dimensions [note 3].

Deterioration is usually understood as loss of information. Paradoxically the very causes listed above may be considered as agents of information enrichment. Total loss excepted, damages may add to the documentary value, being traces of the object's biography. In this respect Monger speaks of 'working appearance' (Monger 1988). Many objects in museums, however, derive their value from the mere fact that they are damaged. These damages refer to important events, such as revolution and war. In this sense Gogelein introduced the term 'historical quality' for the secondary data [note 4].

Deterioration may contribute to the aesthetic value of an object. A certain degree of decay may be intended by the maker as 'finishing touch' applied by Time (v.d.Wetering 1973). In such cases it is the actual appearance rather than the factual appearance that reflects the conceptual identity. In other cases the acquired appearance of the object (the 'patina') may give raise to an aesthetic appreciation that is not connected or even contradictory to the maker's intention [note 5].

The actual identity is a dynamic concept. The object as continuant can be considered a succession of different phase-sortals (Wiggins 1971: 29). Wiggins discusses the case of a ship which is continuously repaired by taking out the old planks and putting in new. Is it, after all the planks are changed, still the same ship? But what happens if somebody had kept the old planks as they were taken out, and by putting them afterwards together in the same order? Is this the same ship or another? According to Wiggins the persistence in form and the spatio-temporal continuity favours the repaired ship as 'original'. In terms of image and substance, it is a continuity of image but a replacement of substance. Important is the assumption that their is a close connection between the original intention and the image.

More complicated is the case of dis-assembling and re-assembling of objects, like machines and buildings. Is the re-assembled object a new object? It is the same material, but there is no spatio-temporal continuity as to image. To some extent we are dealing with a reconstruction, i.e. an interpretation of the original intention. Using the same substance for a new image creates a new object since there is no continuity as to conceptual identity.

From a philosophical as well as a legal point of view actual identity might, however, be considered as representing a different object as the object represented by the factual identity, especially when restoration is involved. Restored objects, although spatially and temporally continuous under the sortal 'object', are not so under the sortal 'maker'. After the nth repair, the restored object is the product of the restorer(s) rather than of the maker. In philosophical terms: this is a case of identity under genus while there is a change in species (Sagoff 1978: 459). In legal terms the object in its actual stage can be considered as 'derivative work' in the production of which the original work is consumed (Mandel 1981). This might have serious consequence for the copyrights. When a restorative intervention involves a significant alteration of the ratio of primary data to secondary data the actual, restored object is - at least according to U.S. federal law - legally considered as copyrightable. This is certainly the case when a restorer puts together archaeological fragments. Such effort may be considered a 'compilation'.

The model introduced above implies a certain continuity as to the object's structural identity. Context transforms, however, may induce significant discontinuities in the physical properties of an object. When an object has lost its practical value (functional degradation) it will be disposed or adapted to be re-used. Re-use may occur as 'total re-use'. This implies re-use without changes, re-use after renewal, and re-use after adaptation. In these cases a clear continuity of the structural identity is involved. Re-use may also occur as 'partial re-use'. This implies re-use of a part of the former object as new autonomous object or the combination of part(s) of the object with other elements in order to create a new object. In these cases there is a clear discontinuity of the structural identity as there are in fact two objects involved. Finally, re-use may occur as 're-use as raw material'. For example, in case of the remelting of metal objects, the original identity of the object is reduced to a minimum. Very often, however, a part of the structural identity of the original object is preserved as part of the primary data, either as intentional information or as non-intentional information.

The model may be applied not only for individual artefacts but also for artefact sets. Accumulation and disposal constitute the process indicated as 'genesis', based on a concept concerning the content (composition) in relation to the function. However, unless there is a break in the continuity, the factual and actual structural identity can often not be distinguished. For example, as long as a room is used by its occupant it is difficult, if not impossible, to define the moment of completion. A clear break in continuity can occur when a new person will occupy the room. Other examples of a break in continuity are natural catastrophes, like earthquakes and volcanic eruptions, and the acquisition of the artefact set by a museum.

1. Other terms used for 'factual identity' are 'Schöpfungszustand' and 'Urzustand' (Wechsler 1987: 97). >back<

2. This list is partly based on Feilden 1979. >back<

3. This 20th century renewal of the church interior led to the disposal of much of the neo-gothic paraphernalia, which in their turn replaced much of the older decorations etc. as result of the religious revival of the 19th century (see Van Leeuwen 1984). >back<

4. in his annual report for the year 1981 of the Rijksmuseum Boerhaave, Leiden. >back<

5. Thus the actual appearance reflects the conceptual identity of the perceived object rather than that of the conceived object. >back<