Among those who are Godless and who are high-church (note that there are plenty of people who claim to be Christians but who are still Godless), there is a sense that anyone who behaves or acts rationally, then they have done good things. Unfortunately, this could not be further from the truth of the matter.
Rational thinking is the ideal state of mind for the post-modern man. It is a mind without sin or at the very least without bad thoughts in the minds of many men. And it occurs in most secular-based philosophies largely because they fail to truly understand what real evil is.
The problem with believing that rational thinking is the perfect state of mind is that mankind bases his reasons on mostly irrational concepts. Philosophies and religions are, by and large, irrational disciplines. But they form the premises of the ideals that men use to rationally think through their belief systems.
Of course, in the belief that rational thinking is good, people tend to also reason that irrational thinking is bad. So when they view religious dogma as irrational, they tend to dismiss the arguments made by religious thinkers because the premise of their arguments are viewed as irrational. Meanwhile, the rational few forget that their own core beliefs are irrational as well, but they view them as perfectly rational because irrational thoughts are bad and their thoughts are perfectly rational.
The truth is, most of the great evils in this world were rational actions brought on by their core irrational beliefs. Communists have murdered millions of people in the last century alone, far outstripping the Christian dominated West of the previous 1800 years in body count. This was all done in the name of stamping out irrational religious and economic thought in their minds. It was done to create Utopia on Earth, to create a paradise for all of mankind to strive for.
But countless wasted lives later, we see that the former Soviet Union is now a shell of what it was with dwindling demographics and lost economic manpower. China is looking at a demographic decline that is even worse. The one thing that communists seemed to forget is that the economy is not an abstract concept that can be managed by a central elite but a vast network of interactions between people. And when you have less people, you have a shrinking economy.
Likewise, the Spanish Inquisition, which claimed the lives of roughly 800 people over three centuries, was a rational response to Islamic aggression on the Spanish peninsula. I won’t go to much into the history of it, but the Spanish crown had just liberated their country from Muslim conquerors and they were not about to let their foes just over the Mediterranean sea reconquer it. Loyalty to the Catholic church was loyalty to the Spanish crown in the minds of the people there.
ISIS (or ISIL) is likewise following a very rational path given their belief system. While it is brutal, disgusting, and horrifying, their actions appears to be directed at creating fear and intimidation in order to save the souls of their fellow countrymen. And honestly, if you felt that murdering a bunch of Christians would cause the rest of the populace would fall in line and thereby secure their place in Heaven, would you not consider it?
Do I agree with all of these things? No, I don’t. But I understand their reasoning, their logic, their rational thoughts.
The point I am trying to make here is that rational thinking is merely how we process our irrational belief systems. From the atheist who claims that God doesn’t exist because babies die to the Catholic who claims that dead babies go to Limbo to myself who believes in God’s good judgment on our hearts, we all share irrational beliefs.
Only a fool would believe himself to be good if they thought and acted rationally. Moral good is an irrational concept just as much as evil actions are. So have a clearly defined moral code (it’s pretty easy if you are a religious person, a non-religious person has a tougher time) and use rationality to dictate your actions based on what is morally good. I recommend you follow Christian virtues and morality, even if you don’t believe in God, merely because centuries of its use has created the greatest civilization the world has ever seen with the least amount of bloodshed.