Simple - what you see as dark and light or positive and negative or good and evil - is just a matter of "you think it there for it must be true". Which is farthest from the truth. If people could understand what the truth really is - we would have World Peace, but that is another matter.
Back to the question - think of it as this - your mind works like this ---- (simplified for dramatic effect - lol)
1. When the consciousness feeds the subconscious – it produces results which in turn feeds the consciousness that expands and exemplifies the results either negatively or positively depending on the over all polarity of the consciousness demands.
2. If the consciousness demands positive or negative results from the subconscious – the subconscious reacts and delivers the results – positive results for positive demands and negative results for negative demands that in turn - see #1.
The subconscious and consciousness each play by their own set of rules. There are conflicts between the two that have to be taken into consideration, but as a whole our minds works on positive and negative polarities that merely and wholeheartedly act like a force of nature seeking the path of least resistance.
Now envision the statement above but Replace -
Positive = Living
Negative = Survival
Meaning - we sometimes confuse survival instincts in the conscious and do really jacked up things when we perceive a threat - real or not. Plus, we justify anything we do with the reasoning - "we think it there for it must be true". Believe me - you can reason yourself into anything - next time your disagreeing with someone - switch sides and you will find yourself just as believable on both sides of the fence. Again - just because you think it or feel it - does not mean it is true, right or good. Here in lies the problem - anyone can be anything if put in the right conditions. People are caught up in good & evil, instead of truth and understanding, and because they are caught up in the Light/Dark or Pos/Neg or Good/Evil - they continue to encourage conflicts within themselves and others.