Sosnowski was an outstanding researcher and expert in Polish architecture and brick construction of the past. He represented progressive scientific thought in this field. It is to him that the revival of inventory and research activities should be attributed, collection and scientific study of material related to the verification of some preserved monuments, and most importantly, the education of many excellent restorers.
Szyszko-Bohusz already in 1913 he presented his thesis, that can be summarized in a sentence: The cardinal principle of conservation should be to strive to maintain the old and collapsing parts of the monument, and any additions should reflect the spirit of our times along with the latest technological achievements.
The above thesis was modified by Lauterbach. According to him, the most rational method of monument conservation should be based on scientific material and improved technology., the shape of the monument cannot be changed or modernized
Other Polish theoreticians, researchers and practitioners represented more liberal views in conservation activities. When preserving and strengthening historic substances, they did not oppose the changes, which should be made due to cultural and civilizational needs, relatively to ensure the stability and durability of the building. Everything though, what needed to be added or changed, it could not violate the historic features of the monument and should be far from any forgery, while its form clearly indicates the time, in which it was created.
The theories and views presented above in the field of conservation of monuments of construction and architecture in Poland had to be thoroughly revised after World War II,
In year 1945 Jan Zachwatowicz (1900—1983) as a general conservator, he specifies the program and rules for the conservation of monuments in the new reality.
The author of the "Program" takes a position on architectural monuments of particular importance to Polish culture, that have been damaged or completely destroyed in the course of hostilities, and also towards these, which were deliberately destroyed in order to obliterate national features or were destroyed as a result of insufficient care in the interwar period.
The basic theses of the discussed "Programme" can be formulated as follows:
— Konserwowane zabytki powinny odpowiadać współczesnym potrzebom życia, without losing its historical and artistic values. To ensure their durability, the methods used should be thoroughly scientific and should use all technical and construction achievements.
— Zburzone zabytki powinny być odbudowane — jeśli potrzeba — od fundamentów, from available materials, with the restoration of forms, which they had, and adapting functions to practical usability.
The above theses were not uncritically accepted. It is understandable, that they are in conflict with their views, especially with orthodox theories propounded in other economic and political circumstances. Currently, however, many years after their publication, that, from the point of view of certain historical facts and patriotic motives, the "Program" rightly set the direction of conservation activities in Poland during the period of reconstruction of the country, because the general public saw in the restoration and reconstruction of old town historic complexes understandable compensation for the damage and losses suffered.
Summing up the considerations on the theoretical assumptions in the field of monument conservation methods quoted in this chapter, it must be stated, that this issue has not been clearly defined until recently. Determining the rules of conduct in this area is still extremely difficult, because, to a large extent, the criteria are an expression of a specific worldview in the field of sociological aspects of culture. Is obvious, that in this discipline controversial positions have clashed in the past, but it must be noted, that they are represented today, despite the development of methods of action. However, it must be stated, that in the premises of conservation proceedings they lost their extreme and doctrinaire positions.