Notable enough, however, are the controversies over the series 1 – 1 + 1 – 1 + 1 – … whose sum was given by Leibniz as 1/2, although others disagree. … Understanding of this question is to be sought in the word “sum”; this idea, if thus conceived – namely, the sum of a series is said to be that quantity to which it is brought closer as more terms of the series are taken – has relevance only for convergent series, and we should in general give up the idea of sum for divergent series.
