AT Robertson on the Genitive
It is that the case does not of itself mean all that one finds in translation. The case adheres to its technical root-idea. The resultant idea will naturally vary greatly according as the root-conception of the case is applied to different words and different contexts. But the varying element is not the case, but the words and the context. The error must not be made of mistaking the translation of the resultant whole for the case itself. Thus in Mt. 1:12 we have μετοικεσίαν Βαβυλῶνος . It is translated ‘removal to Babylon.’ Now the genitive does not mean ‘to,’ but that is the correct translation of the total idea obtained by knowledge of the O. T. What the genitive says is that it is a ‘Babylon-removal.’ That is all. So in Mt. 12:31, ἡ τοῦ πνεύματος βλασφημία, it is the ‘Spirit-blasphemy.’ From the context we know that it is blasphemy against the Spirit, though the genitive does not mean ‘against.’ When a case has so many possible combinations in detail it is difficult to make a satisfactory grouping of the various resultant usages. A very simple and obvious one is here followed. But one must always bear in mind that these divisions are merely our modern conveniences and were not needed by the Greeks themselves. At every stage one needs to recall the root-idea of the case (genus or kind) and find in that and the environment and history the explanation.
- AT Robertson in A Grammar of the Greek New Testament in the Light of Historical Research XI.VIII(c)