{Twofold more a son of hell than yourselves} (huion
geenn(8873) diploteron h(966d)(936e)). It is a convert to Pharisaism rather
than Judaism that is meant by "one proselyte" (hena
pros(886c)uton), from proserchomai, newcomers, aliens. There were
two kinds of proselytes: of the gate (not actual Jews, but
God-fearers and well-wishers of Judaism, like Cornelius), of
righteousness who received circumcision and became actual Jews.
But a very small per cent of the latter became Pharisees. There
was a Hellenistic Jewish literature (Philo, Sibylline Oracles,
etc.) designed to attract Gentiles to Judaism. But the Pharisaic
missionary zeal (compass, periag(8874)e, go around) was a
comparative failure. And success was even worse, Jesus says with
pitiless plainness. The "son of Gehenna" means one fitted for and
so destined for Gehenna. "The more converted the more perverted"
(H.J. Holtzmann). The Pharisees claimed to be in a special sense
sons of the kingdom ( Mt 8:12 ). They were more partisan than
pious. Diplous (twofold, double) is common in the papyri. The
comparative here used, as if from diplos, appears also in
Appian. Note the ablative of comparison h(966d)(936e). It was a withering
thrust.