A child's first experience with mathematics comes from their everyday life. The child does not know what three is but knows what three fingers, apples or candies are. Later, in consequence to abstraction, this semantic anchoring of mathematical ideas is expanded by ideas and concepts that are not directly dependent on semantics. We call this process " desemantization ". If the process of desemantization ousts semantic links from a pupil's mind as a result of too fast a drill of additive and later multiplicative structures, we speak of irreversible desemantization whose consequence is mechanical knowledge of a child. The paper develops this concept.