It is indeed remarkable how strongly a person will believe X is true based on the slimmest (or even complete lack of ) evidence while at one and the same time deny Y is true that actually has empirical and observational evidence in support of it.
Scholastics were medieval theologians and philosophers who focused their efforts on protecting the teachings of the Catholic Church from being challenged and replaced. They never tested anything empirically. Instead, scholastics emphasized the importance of “revealed truth” in figuring out what was right from what was wrong. This means they relied on God Himself to talk to them and reveal truth to them. The problem with relying on revelation was determining whether God was actually talking to you or you were simply talking to yourself. There was no way to scientifically test where the voice (and ideas) were coming from; it was, after all, quite possible scholastics were just convincing themselves God was inspiring them. Ultimately, scholastics had one purpose—to defend Church teachings from challenges by freedom seeking kings, questioning scientists and troublesome philosophers.
Scholastics relied on not only their inner voice but also the use of logic and deduction.  Deduction is a powerful tool because you can use it to create a big idea from little information. For example, in the 20th century we finally had telescopes powerful enough to look outside of our galaxy. A Catholic priest named Georges Lemaître (1894-1966 CE) was the first to notice galaxies were either tinted blue or red. Thus, he deduced light was cast from these galaxies like sound traveling from a car to a person standing still (as in the Doppler Effect). When a car approaches a person standing still the sound is low but when the car passes by the pitch becomes higher. Light, Lemaître deduced, must also change when it is traveling towards and away from us, i.e. if a galaxy was “blue-shifted” it was flying away from the Milky Way but if it was “red-shifted” then that galaxy was flying towards us. Deduction, as illustrated in the example above, can be quite a powerful tool; however, it is not without its problems.
Anselm of Canterbury (1033-1109 CE) was an important scholastic and theologian who was responsible for creating something fancy called the “ontological argument” for the existence of God. The word ontology has Greek roots and is roughly equivalent to the English word necessity. Anselm deduced that it was necessary God exist. He reasoned that he could picture the most perfect and powerful being in his mind. The only way this was possible was if God actually existed (because, Anselm argued, the concept of a God had to point to the object God). In other words, it was necessary God exist because otherwise a concept of this being would not be possible. The problem with Anselm’s argument is it is easily disproven. Another thinker came along about 150 years later named William of Ockham (1285-1347 CE). William, like Anselm, was a theologian and worked for the Church. William, however, unlike Anselm was not made a saint by the Catholic Church. Instead, William was persecuted for doing things like absolutely disproving Anselm’s proof for the existence God. Specifically, William reasoned he could conceive in his mind of the most perfect and powerful unicorn; however, he concluded that just because he had a concept of a unicorn in his mind this didn’t necessarily mean the unicorn actually existed; and that’s the problem with scholasticism, really: it was never based on evidence, it was based on a series of self-reinforcing assumptions about reality.
In the 17th century, the Church was successfully challenged by scientists and philosophers. Science represented a new way of looking at the world. The scholastics looked at the world spiritually; they explained the word spiritually. Scientists looked at the world materialistically and explained physical reality by appealing to laws of nature rather than to a God pulling strings behind the scenes. Scientists didn’t rely on revealed truth like scholastics; rather, they literally tested their assumptions against physical reality; it was the work of early scientists, like Galileo Galilei (1564-1642 CE) and Isaac Newton (1643-1727 CE), who nudged science in the direction of finding patterns in nature; and from these patterns they developed laws like the Law of Gravity, the Law of Planetary Motion and the Laws of Thermodynamics. The Church was also challenged by modern philosophy because philosophers like Rene Descartes (1596-1650 CE) and John Locke (1632-1704 CE) encouraged people to “doubt systematically.” When someone doubts systematically they ask a series of questions, and conduct a series of logical tests, to determine whether or not a belief is valid or if it is fallacious. The best philosophers, like Descartes and Locke, also used scientific knowledge to inform their thinking. This is because intellectuals were more focused on finding patterns in nature, patterns in human societies, etc. and from these drawing conclusions about their meaning and significance. Scholastics, on the other hand, started with the meaning and significance and then explained what they saw.
Humanist philosophers used logic and deduction, as well. However, while scholastics designed arguments simply to defend Church teachings and authority, humanists were motivated out of a genuine desired to describe and understand truth for its own sake. This doesn’t mean humanists did not believe in God; on the contrary, virtually every humanist, scientist and philosopher during the Scientific Revolution and Enlightenment periods believed in God. God wasn’t in question. The Church’s doctrines, teachings and authority were; and the Catholic Church’s authority gradually grew weaker and weaker over time.
 Testing something empirically means testing it by means of observation or experience rather than through theory or pure logic.
 When we only have a little bit of information we use deduction to work from what little we do know to create a larger picture. The problem with this approach is it requires a lot of imagination and basically no testing or experimentation. Aristotle, for example, used deduction to explain why objects “fell” downwards. He didn’t appeal to the existence of gravity but instead deduced it is in the nature of an object to “want” to fall down. The strange thing about thinkers before the Renaissance and the Scientific Revolution is they believed objects actually had intentionality, e.g. magnets were explained as not being attracted due to a force called magnetism but that they had “souls” that sought one another out.