A strong debate between science and faith has been going on for many centuries. Galileo was persecuted for standing behind is belief in heliocentrism. Currently religious figures and scientists dispute the earth's creation. Were humans created by God just as they are now, or did they evolve over millennia? Questions like these make it easy for one to think reason and faith contradict each other. However, Thomas Aquinas firmly believed the two work in harmony and enhance each other. He explains this in his "Suma contra gentiles."
In the 1600s Galileo presented evidence for heliocentrism, the idea that the earth revolves around the sun. Using a telescope he invented, Galileo made more detailed observations than ever before possible. His observations led him to realize that contrary to popular belief, the sun did not revolve around the earth. In fact, he found the sun to be the center of the solar system. Despite his sound data, Religious leaders refused to accept the theory because they felt it conflicted with scriptures such as Chronicles 16:30, Psalm 93:1, Psalm 96:10, Psalm 104:5, and Ecclesiastes 1:5. Galileo held fast to his beliefs, refusing to recant his statements, was persecuted as a result, and sentenced to death. Clearly, because heliocentrism is now taught in schools the church eventually experience a change of heart.
More recently, an important argument has revolved around creation. The book of Genesis tells that God created the earth in seven days. On the first day he created light; on the next, water. Third, he separated land from sea and created vegetation. By the end of the sixth day he had created Adam and Eve. From the first two human beings, the bible follows the stories of their descendents. When all of this is interpreted literally, as it is with most Christians and Jews, the timeline makes earth to be around 6,000 years old. Scientists argue this cannot be true. Using carbon dating and evaluating layers of the earth's crust they have compiled data that says the earth must be over 4 billion years old. Evidence of dinosaurs and an ice age serve as compelling evidence to a time when humans did not walk the earth. Seemingly these two points of view are at odds. Can they be viewed through a lens in which they work together?
Thomas Aquinas would argue that there is. His strong belief was that truth comes from God and any truth arrived at by humans cannot contradict Divine truth. If what we conclude through careful reasoning is true, it will not contradict God's revelation. In the case of creation, both parties may be arguing "facts" that are untrue. For instance, the Bible may not mean that creation happened literally in seven days. It could refer to days in God's time or perhaps describing the process in days was the only way people could comprehend the story at that time. On the other hand, scientists may be using carbon dating incorrectly. Carbon dating is based on the rate at which carbon decomposes. Using other elements, the way elements commonly decompose was established and the rules were transferred to carbon. It is possible carbon decomposes differently. No one can know it is accurate beyond doubt because that would require precise measurements over an extremely long period of time, and carbon dating technology is only a recent invention. With these thoughts in mind, it is entirely possible that both parties are incorrect to a certain degree, due to human error.
Aquinas said that through reason one can come to know that God exists. However, there are many reasons one would not come to know him without revelation. First of all, it requires a great deal of knowledge about the world and deep understanding. Some people do not have the intelligence necessary. Additionally, such study entails much time and great effort. Not everyone can devote their life to such study because they have other obligations to attend to: families, jobs, etc. On top of that, humans are fallible. Their reasoning is sometimes faulty and they easily jump to conclusions. Unfortunately, this means only a few people would come to know the truth. Thus God revealed his nature to humankind so that all may know Him. In this way people are not led astray by their own imperfect reasoning. They can compare what they reason to be true with that which God revealed to us as a way to evaluate accuracy.
It is easy to get confused by seemingly contradictory evidence. Using what one believes to be sound reasoning, one can arrive at incorrect conclusions. However, God gave people the ability to reason and by diligently examining perceptions one will find that faith and reasons do not contradict each other.