The aim of this master’s thesis is to examine which ideas about the public library that appear in a selection of municipal library plans and to examine if these ideas are unanimous. The comprehensive questions are: Which ideas about the public library appear in each municipal library plan? How do the ideas agree in the different municipal library plans? The sub questions are: Which judgements of reality appear in the different library plans concerning each municipality and its library needs? How do the municipalities define the concept of development and future demands in the municipality on the basis of the judgements of reality? Which recommendations do the judgements of reality give and how is the plan of action that is established in each library plan justified? Which fundamental views of reality, i. e. which values of the library and its role (function, task and responsibility in the municipality), do the library plans contain? The theoretical basis of the study is a model, designed by Dorte Skot-Hansen, consisting of three rationalities – humanistic, sociological and instrumental - that constitute the cultural policy. Idea analysis is the textual analytic method used in this study to classify the material and make visible the ideas in the library plans. The concept of the idea consists of the three elements: judgement of reality, recommendation of action and a fundamental view of reality. A modified version of Skot-Hansen’s model is used as a means to analyze the empirical material, which consists of six library plans. The findings of the study show that each library plan manifests all of the rationalities and that the ideas about the library that appear in the selection of library plans are practically unanimous.