There are many ways of approaching Husserl’s philosophical works and it is most usual to start with those of his mature period. One is then confronted with notions specific to his philosophical thought enhanced by a technical terminology linked to his desire for accuracy in the expression of ideas (epoche, phenomenological reduction, eidetic knowledge, intentionality, noeme-noese, etc.) In a first attempt to approach Husserl, it may be wise to follow him step by step in his initial research about the essence of number. It means then “going back to what constitutes the thing itself” and examining it until reaching “the primeval evidence” which helps under-stand the logical and psychological possibility to construct it. If the “class” that constitutes the number stems from experience, it will be wrong to reduce it entirely to its sensitive characteristics. The “cardinal mistake” of empiricism consists in wrongly reducing the numeric given to the empirical one. The number involves a “collective linkage” which requires an actual construction work.