I first learned about the idea of "Spirit nature versus sinful nature" during Bible study my Freshman year. At that time and since then I have brought it up with many religious people, and after conversing on the subject I always find myself very frustrated, if not angry. I don't use the word "hate" too often, but this concept is probably the one thing I hate most about Christianity. It is the worst combination of being a commonly held belief and having severely negative implications for the perception of non-theists around the globe.
Here's a brief summary of the idea: Before we are "born again" (accept Jesus in our hearts, become Christian, etc.) we only possess the sinful nature. Once we are born again we accept the Holy Spirit, and can then fight the sinful nature by filling ourselves with the Holy Spirit. So, if you don't want to lead a life of sin, you MUST be Christian. If you don't see why this view might be troublesome you aren't looking hard enough.
The problem only becomes compounded when we take even a short glimpse of what exactly Holy Spirit nature and sinful nature consist of. I'm taking a look at Galatians 5:16-26, for reference:
"16 So I say, walk by the Spirit, and you will not gratify the desires of the flesh. 17 For the flesh desires what is contrary to the Spirit, and the Spirit what is contrary to the flesh. They are in conflict with each other, so that you are not to do whatever[a] you want. 18 But if you are led by the Spirit, you are not under the law."
Note the use of opposites here (Christianity tends to deal in absolutes, especially when compared to Eastern religions, which are much more complex in their understanding of the way the world works). On one side there is the Spirit, on the other side flesh. One is good (perfectly good, as a matter of fact) and one is bad. It is that simple. Guess which is which? Also note that last bit about being above the law when doing Holy acts. That's reassuring.
Next Paul kindly explains to us what he means when he says "acts of flesh," since, you know, if he was too vague people might interpret things the wrong way:
"19 The acts of the flesh are obvious: sexual immorality, impurity and debauchery; 20 idolatry and witchcraft; hatred, discord, jealousy, fits of rage, selfish ambition, dissensions, factions 21 and envy; drunkenness, orgies, and the like. I warn you, as I did before, that those who live like this will not inherit the kingdom of God."
Let's start with the first one. What the Bible just told us is that acting on any sort of sexual desire is sinful. Sorry biology, the God who created you doesn't want you to act on those strong impulses he gave you (by having your body create testosterone and other hormones). Oh, and, sorry, but the only way to not act on those biological impulses is to accept Christianity and fill yourself with the Holy Spirit. And did I mention that if you do act on those impulses without accepting Jesus you're going to Hell forever? That's important. Like, of all time importance.
This may be controversial to say, but I think that one of the reasons it's sometimes so difficult to truly understand the commonly held Christian worldview for the nonreligious (and why that worldview causes so many problems in the eyes of atheists) is because, to put it simply, Christians have a very different perception of what is right and wrong. For them, things that are wrong are things that are sins. This might be acceptable, if the Bible wasn't such a crappy moral compass when read thoroughly. Selling your daughter to slavery is OK in God's book (unless he changed has changed his mind on what is sinful since the Old Testament, which as far as I'm aware is not something omniscient beings do too often), while two guys in a relationship enjoying anal sex will earn themselves two free tickets to an eternity in Hell.
This does not hold true in an atheist world view for the simple reason that there is no rational justification to believe that slavery is more moral than consensual sex. And if a Christian agrees with this atheist worldview they would have to admit that not all sins in the Bible are bad (such as those that don't harm anyone involved), in addition to agreeing that the Bible is a document that contains laws that we should be actively opposing in any moral society.
Now let's take a look at the rest. The first passage specifies that without accepting Jesus and the Holy Spirit into your heart you ONLY have the sinful nature. Which means that this second passage specifically tells us that atheists are more likely to hate, be jealous, have fits of rage, selfish ambitions, and dissensions, among other great qualities (as quoted in the bible verse above). Although I think even Christians will agree that we tend to keep the witchcraft and idolatry to a minimum.
|I might as well be this guy.|
But seriously, you wonder why 55% of the country would never vote an atheist for President? It's because of this. This is what many Christians think we are, or at the very least are inherently more likely to be than they.
For no other reason than the fact that we have a different set of religious beliefs.
One last part here to touch on before Bible study finishes:
22 But the fruit of the Spirit is love, joy, peace, forbearance, kindness, goodness, faithfulness, 23 gentleness and self-control. Against such things there is no law. 24 Those who belong to Christ Jesus have crucified the flesh with its passions and desires. 25 Since we live by the Spirit, let us keep in step with the Spirit. 26 Let us not become conceited, provoking and envying each other.
Ever hear a Christian sincerely ask something along the lines of, "If you don't believe in God, why don't you just go murder people and steal everything?" Those are usually the ones you respond to by saying, "You know, maybe it's best you stay a Christian..." It's scary that, for them, their religion is all that's keeping them from going on murderous rampages. Yet we know that isn't actually true- I doubt that before they were religious they murdered people on a whim. It was a belief they came to accept over time. And this is why they believe that. The fruit of the Spirit is love, joy, peace, kindness, and goodness. To them it only makes sense that without the Holy Spirit you might as well just be murdering people.
"We Christians aren't perfect either," You may hear. "I don't judge others, that's for God," I've heard multiple times. But until you accept the Holy Spirit, in their eyes you're going to be hopeless, full of envy, full of jealousy, and full of hatred; in short a life doomed to sin.
And remember, it's not them judging you. It's just what they believe about people who are different than them.