The paper addresses the way in which modern linguistics, -- in particular, but not exclusively, the generative tradition --, has constructed its core concepts. It argues that a particular form of construction, reminiscent of, but crucially different from, abstraction, which is dubbed ''idealisation'', plays a central role here. The resemblances and differences between abstractions and idealisations are investigated, and consequences of the reliance on idealisations are reviewed. [ABSTRACT FROM AUTHOR]