Penelope, thank you for this question. I am more used to being ignored than having to defend a claim I make, so I do appreciate your comment. I think Conrad is critiquing these Victorian values which you imply he shared. 'Shielding' ourselves from nature results in distorted pathologies, with the prime example the Genesis calls to subdue and multiply. Conrad is drawing attention to the modern consequences of the unthinking use of this biblical myth. My view is that one of the important lessons of HD is that truth (ie God) appears more within nature than within the human effort at control. The Congo River is morally superior to the King of Belgium.
I will take relevant HD quotes from those I cited at http://www.booktalk.org/heart-of-darkness-t4250-40.html
page 5, posted 2 Feb.
"the silent wilderness surrounding this cleared speck on the earth struck me as something great and invincible, like evil or truth" p33
"Going up that river was like traveling back to the earliest beginnings of the world, when vegetation rioted on the earth and the big trees were kings." p48
"stillness of an implacable force brooding over an inscrutable intention" p 48
"inner truth is hidden, luckily, luckily, but I felt it all the same" p 49
The way I read these comments is that Conrad is presenting a critique of mainstream European thought, especially Hobbes' claim that the life of nature is nasty brutish and short. JC's experience of Africa suggests a vision of nature as "great and invincible", words which apply more to truth than to evil, perhaps a deliberate irony. It is interesting that Conrad gives us this choice though