One of the first Calvinist authors I read thoroughly was Jonathan Edwards. He was much derided in my high school American Lit class for the hellfire of "Sinners in the Hands of an Angry God", but he wrote hundreds of other books and sermons as well. His Freedom of the Will is an epic logical tome of metaphysics, in which it is explained that we do things because of our nature, and our wills are bound to that nature. In Calvinist speak this deals with the Sovereignty of God and the depravity of man. Despite the fact of our moral instincts, there are sociopaths who lack this instinct on one hand, and on the other none of us complies with our instinctual morals perfectly (white lies, outbursts of rage in an otherwise gentle soul, etc.)
But neuroscience shows that things we do are a product of biology, chemistry, physics. I have some disagreements with Sam Harris, but this area in particular is his expertise.
Natural revelation teaches us that whatever we learn from nature is in fact not a deception, but is truth. You can look at a deer and an elk and figure out that they are more closely related to each other than a cat and a frog. You can sail around the world and figure out the earth is round. (If that doesn't work for you, take a rocket ship and look at it from space.)
Natural Law teaches us that the moral law is not something that has to be imposed on mankind by an external force, but is something that is inherent to our nature. According to Reformed doctrine, the sin of Adam was a failure to obey the Moral Law.
Paul says it's "written on our hearts."
Sam Harris says this morality predates homo sapiens, and that our closest living relatives, the chimpanzees, share the morals summarized in the second table of the 10 Commandments as well (apart from the prohibition of coveting).
In other words, we didn't need Moses to go up Mount Sinai to figure out that killing and stealing are wrong.
This framework made famous by the Lutherans and adopted by the Reformed communions is a very helpful way to discern critically whether a given command from Scripture is binding or not. Basically it goes like this: God made a covenant "of works" with Adam which Adam broke. In his covenant with Abraham in Genesis 15 (the covenant of Grace), Yahweh explained that the onus was on himself to fulfill the terms of the covenant, unconditionally. (This is what was signified by Yahweh passing between the animal parts. The party making the oath is saying "Be it done so to me if I fail to keep it.") When Israel ratified the covenant at Sinai it was a ratification of the covenant of works. The entirety of the Mosaic Law is a man-made religion endeavoring to pull themselves up by their bootstraps, with the exception of the Ten Commandments themselves. The Law consists of three parts: the ceremonial law, the civil law, and the moral law. The Moral Law is "summarized" in the Ten Commandments but is also "written on the hearts of men." The civil law was particular to the now-extinct kingdom of Israel (eye for an eye, etc.) and the ceremonial law (priestly duties, sacrificial system, etc.) was "fulfilled" in Christ as all the blood sacrifices were a foreshadowing of what was to come in his ultimate sacrifice in which the covenant of grace was fulfilled (as Jesus/Yeshua being Yahweh incarnate paid the ultimate price himself).
In the Lutheran view anything that is commanded for us to perform is law, and everything that scripture says God does for us is "gospel". This is the case whether the verse being referenced is in the old or new testament. Moral law (as opposed to civil or ceremonial) is still binding, but it doesn't elevate us in any way. Our salvation is wholly upon God's grace in the gospel.
The problem is that Presbyterians and Lutherans make up only a tiny percentage of the number of Christians in this country, and among those in their ranks, the percentage who actually know and understand these doctrines is likewise miniscule. This means that most who identify themselves as conservative Bible-believing Christians are not interpreting scripture through these lenses and take single verses (such as "homosexuals are an abomination") as God's holy word and somehow forget that Jesus said "he who is without sin cast the first stone." (You'll hear me discuss this elsewhere under the umbrella of "Theodicy.")
Mahavira, the Jain patriarch, surpassed the morality of the Bible with a single sentence: “Do not injure, abuse, oppress, enslave, insult, torment, torture, or kill any creature or living being.” Imagine how different our world might be if the Bible contained this as its central precept. Christians have abused, oppressed, enslaved, insulted, tormented, tortured, and killed people in the name of God for centuries, on the basis of a theologically defensible reading of the Bible.
Excerpt From: Harris, Sam. “Letter to a Christian Nation.” Knopf, 2006-09-19. [iBooks] (https://itunes.apple.com/us/book/letter-to-a-christian-nation/id419966352?mt=11)
If you grow up in a Pentecostal, charismatic, or semi-charismatic church, you have likely had certain experiences which you perceived to be spiritual. You felt the "tug" of the Holy Spirit on your heart, or his prompting you to pray for somebody in a certain way out loud, after which the person you were praying for is like, "Wow, that was totally God!" Or speaking in tongues. Or when you fell on your back during afterglow and couldn't get up because God was sitting on your trunk. When you give your testimony, you look for those personal "encounters" where you totally felt the spirit move, because these experiences made it "real" to you. You felt like you had a firsthand encounter with an actual invisible spiritual realm.
If you start in charismania and then move to a more Reformed theology informed by scholarship and reason, you end up with rational and theologically sound arguments for what's termed "cessationism". This is the doctrine that the so-called "gifts of the Spirit" were for a certain time and place, namely in the first century, such as in the book of Acts when the gospel was spreading to new regions and signs and wonders needed to accompany the message.
So, how then do you explain all those experiences you had?
On one hand, Reformed theology is probably the best way to make sense of the Scriptures. On the other hand, the "experiences" of the charismatic religions experiences are the biggest hindrance to unbelief, because without being informed by neuroscience, you were certain they were real.
Well, it turns out that neuroscientists can measure this with brain scans. They've been able to determine that praying, speaking in tongues, meditating, etc., all have the same effect on the brain whether one is Christian or another religion. You can perform scientifically experiments on your spiritual experiences and see that they're not spiritual at all.
An English mentalist named Darren Brown did a show called Miracle where he was able to recreate the experiences of faith-healing, tongues, falling on the floor, etc., using the power of suggestion.