Note Footnote 2: — Chapter IX

Technically speaking, if we extend the name Modality (see p. 78) to any qualification of the certainty of a statement of belief, what Dr. Venn here desiderates, as he has himself suggested, is a more exact measurement of the Modality of propositions. We speak of things as being certain, possible, impossible, probable, extremely probable, faintly probable, and so forth: taking certainty as the highest degree of probability2 shading gradually down to the zero of the impossible, can we obtain an exact numerical measure for the gradations of assurance?