Select the allusion in the passage. The engineer had listened to the enthusiastic sailor developing these imaginative
projects. To attack this mass of granite, even by mining, was a Herculean task, and
it was truly vexing that nature had not helped them in their necessity. But he
answered Pencroff, simply by proposing to examine the wall more attentively, from
the mouth of the river to the angle which ended it to the north.

The main themes of the play are: fate and free will with the inevitability of oracular predictions is a theme that often occurs in greek tragedies the conflict between the individual and the state similar to that in sophocles’ “antigone” and   people’s willingness to ignore painful truths both oedipus and jocasta clutch at unlikely details in order to avoiding facing up to the inceasingly apparent truth and sight and blindness the irony that the blind seer tiresius can actually “see” more clearly than the supposedly clear-eyed oedipus, who is in reality blind to the truth about his origins and his inadvertent crimes.