"The presented research project is devoted to the concept of natural number. We will be studying this concept from two different perspectives: the philosophy of mathematics and cognitive sciences. The underlying hypothesis is that in general these two disciplines function independently and do not exchange in an efficient manner.The main objective of the project is to establish a framework of possible cooperation of the to disciplines. The realisation of this objective is twofold. The first aspect is theoretical and (i) begins with a critical study of the up-to-now use of the results of one discipline by the other, (ii) then proposes a conceptual study of the resulting data and (iii) advances criteria for the fruitful use of multidisciplinary knowledge. The second aspect of realisation of the project consists in series of personal interactions with researchers in both, philosophy and cognitive sciences.We argue that the common language and a common curriculum can be elaborated for these disciplines, and that a research conducted in taking into account this common background will largely contribute to the overall understanding of the concept of natural number."