Sui-generis meaning

Yet while, in its application to history, Hegel's theory of evolution has points of resemblance with those doctrines which seek to explain the worldprocess as one unbroken progress occurring in time, it constitutes on the whole a theory apart and sui generis.

Those Cestodes which possess no very distinct organ of attachment (such, for example, as Gyrocotyle) have no distinct ganglionic thickening more pronounced at one end of the body than at the other; and as these are forms which have retained more primitive features than the rest, and show closer affinity to the Trematodes, it seems highly probable that the complicated nervous thickening found in the scolex, and often compared with the " brain " of other Platyelmia, is a structure sui generis developed within the limits of the sub-class.

This is why Moore's own view of goodness as sui generis and irreducible is supposed to avoid the naturalistic fallacy.

He was a deeply religious man, but his exemption of Jewish origins from the canons of historical inquiry which he elsewhere applied was probably due to the conditions of his age, which preceded the dawn of Semitic investigation and regarded the Old Testament and the Hebrew religion as sui generis.