The idea/expression dichotomy represents a foundational concept of copyright. Yet, the boundaries of such a principle tend to be blurred by its inconsistent application, with regard to both subject matter and case law analysis. On the one hand, for certain categories of works, it is objectively difficult to draw a clear-cut distinction between ideas and expressions, as these closely interpenetrate each other. On the other hand, as the result of a more general trend in intellectual property, copyright protection has been extended to categories of works for which the value of expression, as a category distinct from ideas, is low and it is therefore difficult to distinguish a clear application of the idea/expression dichotomy. Furthermore, the dichotomy does not seem to represent a useful tool for courts to rely upon in assessing controversial cases. The present work shall attempt to explore the nature and the boundaries of the idea/expression dichotomy, in particular its reliability, as well as determine whether such a principle can be still considered to be among the foundations of copyright rationale and scope of protection.