 However useful it may have been in practice, the concept of infinitesimal could scarcely withstand logical scrutiny. Derided by Berkeley in the eighteenth century as “Ghosts of departed Quantities” (1734: 59), in the nineteenth century execrated by Cantor as “cholera-bacilli” infecting mathematics (1893 [1965: 505], translated by Fisher 1981: 116), and in the twentieth roundly condemned by Bertrand Russell as “unnecessary, erroneous, and self-contradictory” (1903: 345), these useful, but logically dubious entities were believed to have been finally supplanted in the foundations of analysis by the limit concept which took rigorous and final form in the latter half of the nineteenth century. By the beginning of the twentieth century, the concept of infinitesimal had become, in analysis at least, a virtual “unconcept”.