Read the following excerpt from Joseph Conrad's Heart of Darkness:
I avoided a vast artificial hole somebody had been digging
on the slope, the purpose of which I found it impossible to
divine. It wasn't a quarry or a sandpit, anyhow. It was just a
hole. It might have been connected with the philanthropic
desire of giving the criminals something to do. I don't
know.
Which idea about colonialism is most clearly expressed in this excerpt?