The impossibility of establishing a universal scale of Lewis basicity does not prevent the determination of the quantitative behavior of Lewis bases, thanks to scales constructed against particular Lewis acids: BF[subscript 3], 4-FC[subscript 6]H[subscript 4]OH, I[subscript 2], Li[superscript +], Na[superscript +], K[superscript +], Al[superscript +], Mn[superscript +], CpNi[superscript +], and CH[subscript 3]NH[subscript 3][superscript +]. These scales encompass important types of bonds formed in a Lewis acid-base adduct: the dative bond, the conventional and ionic hydrogen bonds, the halogen bond and cation-molecule bonds for metal cations of groups 1, 7, 10, 11, and 13. Moreover, although these scales are generally not interrelated, there exist family-dependent relationships that permit ranking, in a rather general order, of bases belonging to a given chemical family, for example, the family of oxygen bases. Therefore, the skepticism about the quantitative usefulness of the Lewis concept of acids and bases is no longer founded. (Contains 5 figures.)