One of the many arguments I had with my father concerned evil thoughts, or rather what are considered evil thoughts.  Usually, with dad, it meant sexual thoughts, lust.  He was a demon on lust.  It bothered him continual that people get horny.
 His position was that having a sinful thought was as bad as actually committing the sin.  If you saw a pretty girl and the thought of jumping on her, stripping her and so on entered your head it was evil as actually doing it.  My position was and is that if such thoughts occur to you denying them is a greater feat than never thinking evil at all.
 I was thinking of this recently while reading the Buddha speak of having purity of mind.  I still can't help but think that if your virtue is never challenged how can you know if it's real or not.  That if you think of sin, are tempted but turn it away you are a better stronger human than those with virtuous thoughts only.  Rather like karma, you build virtue as you go.
 I once said that I didn't know how Christians ever knew if they were good people or not.  If you do good in fear of Hell or hopes of Heaven it's not a good deed but an investment in the future and selfish.  In the same way how can you know how good you are if you are never tested?  To prove our mettle we must face life with all its stinks and garbage and stand proof against it.