Ok, this comes from Joseph Conrad's Heart of Darkness (which i did as my related for discovery).
It is easier to understand the quote when you look at it in context. It is:
"...You can’t understand. How could you? - with solid pavement under your feet, surrounded by kind neighbours ready to cheer you or to fall on you, stepping delicately between the butcher and the policeman, in the holy terror of scandal and gallows and lunatic asylums - how can you imagine what particular region of first ages of man’s untrammelled feet may take him into by the way of solitude - utter solitude without a policeman - by the way of silence - utter silence, where no warning voice of a kind neighbour can be heard whispering of public opinion? These little things make all the great difference. When they are gone you must fall back upon your own innate strength, upon your own capacity for faithfulness. Of course you may be too much of a fool to go wrong - too dull even to know you are being assaulted by the powers of darkness.
I take it, no fool ever made a bargain for his soul with the devil: the fool is too much of a fool, or the devil too much of a devil - I don’t know which. Or you may be such a thunderingly exalted creature as to be altogether deaf and blind to anything but heavenly sights and sounds...But most of us are neither one or the other...And there, don’t you see? your strength comes in, the faith in your ability for the digging of unostentatious holes to bury the stuff in - your power to devotion, not to yourself, but to an obscure, back-breaking business. And that’s difficult enough..."
When you read the paragraph above in it's entirety it becomes self-explanatory. But basically it's saying that if you are a fool, you will be too foolish to realise evil, and therefore will not follow down a path of evil. Or if the fool is not too foolish, then the devil is too evil to be realised, meaning the path will not be followed. This is slightly confusing, but that's because both concepts are intertwined. The fool is too foolish to understand the evil which is too evil. (E.g. I am too foolish to understand 4U maths, and 4U is too difficult to understand)
Hope this makes sense
Don't be too fussed as all you need is a loose understanding of this to metaphorically use in your creative, which is under the theme of power?