 Now that we've seen that it can be pretty hard or even impossible to establish if something is indeed true but that trying to falsify claims can help us understand the world, let's take a look at how we can rely on the things we think are not false. Let's first consider the invention of the wheel. Arguably, the wheel is one of the most impactful human inventions and we have tested and optimized it. The wheel is a very sophisticated piece of technology and that's why the phrase you don't need to reinvent the wheel makes so much sense. Let's say you wanted to invent a wheel that can be used for a very specific purpose such as for race cars, high-speed bikes, heavy trains, landing jumbo jets and so on. In this case, you wouldn't have to reinvent the concept of the wheel first in order to be able to develop it further. Instead, you can rely on the general principle of what a wheel is and then build on it. This intuition of relying on things that work without having to reinvent them time and time again is at the core of philosophical approaches that deal with paradigms, research programs and research traditions. They too hold that once you have established that something works or more specifically it is not false. Then you don't have to prove it again and again if you want to do something new. The idea is that we can rely on things we already knew are probably not false. That means once we've corroborated a certain theoretical speculation, we can integrate it into our belief system and keep using it without having to reexamine this principle time and time again. Instead, we can refocus our resources on building on this corroborated idea. These systems of effects, questions and research practices rely on are referred to as paradigms, programs and traditions, a terminology introduced by philosophers such as Thomas Kuhn. Another way to think about such paradigms is as a set of knowledge you carry with you when you go on vacation in a foreign country with a very different culture. You already know some things about how people interact with each other, which helps you recognize behaviors in this new culture again. Although you might be used to people greeting each other with a hug, you might be able to recognize that a behavior constitutes a greeting even if it looks very different. Let's say if people rub their noses. If you rely on a paradigm that makes it easier for you to see instances of certain principles in this paradigm applied to different situations. While it's definitely efficient to accept some things as established, corroborated and traditionally agreed upon, there are some struggles associated with paradigms and traditions as well. First, consider that rejecting an established paradigm may not be well received. If you criticize and attack a central tenet of what's regarded as an established theory, those uphold the theory may not be welcoming of your criticism. Think of an example where we use a certain belief system in everyday life, which is traditional and well established. Many things come to mind. Now consider how the supporters of this belief system would react if one is critical of its central pillars. For instance, imagine what would happen if you criticize the existence of money and you wanted to abolish it. How would people react who've relied on the use of money all their life and worked hard to amass it? There are many examples where we can witness difficulties to depart from what appears to be an established paradigm, from legalizing gay marriage to welcoming refugees. Now, this example doesn't necessarily have much to do with truth, but it helps illustrate why it can be difficult to change existing paradigms. When it comes to science and asking about truth, we have seen extreme paradigm shifts in how we think about the world. Consider that draining blood from the bodies of sick people used to be the most common medical practice performed for centuries, because the then accepted belief about health held that imbalance of bodily fluids was the cause of illness. Today, bloodletting is only performed when indicated by a few very specific diseases and it's otherwise considered pseudoscience. But imagine how tough it must have been to challenge this paradigm about bodily fluids if everyone believed it for centuries. So tough, in fact, that bloodletting is practiced in alternative medicine until today, even though it has been shown that it's actually harmful to drain blood in cases other than the few illnesses where it is required. Typically, it takes more than one challenge of a paradigm until it will be abandoned, and also a viable alternative paradigm to switch to. Sometimes it can take an outright crisis to foster paradigm shifts, which are basically a form of revolution of thought. In addition to stifling criticism, paradigms and traditions can become problematic when they restrict the types of questions you can ask and the types of questions that you can get answers to. You probably know the saying that if all you use is a hammer, everything starts looking like a nail. This principle might also hold for paradigms and traditions. If you only look at the world through the lens of your particular research program, you could miss out on questions that lie slightly outside your field of sharp vision, and the answers you give may be different depending on which glasses are used to find them. To illustrate the first point that you may not ask certain types of questions, let's go back to our logical positivists and deduction. That is drawing conclusions from the true statements. If you only use deduction and you don't ask inductive questions, you would be quite restricted in the way you look at the world. The tools incorporated into the paradigm of deduction cannot be applied to inductive questions. To illustrate the second point that the answers you give to a question will be different depending on the paradigm you rely on, let's consider another example. In North American culture, let's say that's our paradigm, putting a child on the head or tuzzling their hair is used as a sign of affection. In a different paradigm, let's say that of Sri Lanka, the same behavior would be considered highly invasive and rude as the top of the head is considered sacred. In another example, Germany is well known for its cuckoo clocks. And such clocks make popular tradition inspired gifts. However, many Chinese people would consider receiving a clock as a curse, as the phrases for giving a clock and attending someone's funeral sound alike in Cantonese and Mandarin. Depending on your paradigm, the same behavior could be seen as an affectionate gesture or an insult as a nice gift or a curse. Now, of course, in these examples, there is no objective truth about what these gestures mean. It's all about the social norms you're used to. But this goes to illustrate that the paradigms you're used to can influence how you interpret the world, also when it comes to truth. If you'd like, you could pause the video here and do the following exercise about paradigms and traditions. Instead of focusing on scientific paradigms and traditions in this exercise, I'd like to invite you to focus on your personal everyday paradigms. I'd like to ask you to assess the way you are thinking and see if it might be the case that you follow your own personal tradition of thought. First, identify a way of thinking you use in everyday situations. These could be things like your political beliefs, your beliefs about gender, your beliefs about veganism, or religious beliefs. Then ask yourself, how you would react if someone challenged this belief? How would you react if someone told you that the way you were thinking through the lens of this specific belief was limiting and that you were missing important aspects outside of the field of vision that your belief system grants you? Finally, ask yourself if this might mean that your beliefs tempt you to treat everything as a nail. Meaning that you might see manifestations of your beliefs proven, proven right, although that is not necessarily the case. Now, let's turn to another exercise. To understand better how paradigms and traditions influence the way we see the world, research a historical paradigm that was used in an area of science that you are interested in. For example, you could read up on the theory of bad ether being the cause of diseases, the ether theory in physics or about phrenology, the theories in psychology that ascribed personality differences to body types or bulges in the skull. Find out if this way of thinking was used in related areas as well, for instance. Was bad ether also thought to be the cause of mental disorders? Were differences in body morphology also thought to be the cause of other psychological functioning? Let's say of things such as intelligence. Then find out how this paradigm was challenged. What arguments did opponents of this view use to convince others that it was not a description of reality that actually worked? And finally, how was this area of science revolutionized? Which other paradigm gained popularity instead? In this part of the course, we have taken a look at how to rely on existing theories, paradigms, and research programs. We have seen that it makes sense to accept that some parts of our knowledge seem to be not false and to integrate them into a paradigm or tradition. At the same time, we have seen that relying on such paradigms too much can be problematic because we may not be able to shake them again. And we may use them even if it's not actually appropriate. This concludes this chapter of this course. Overall, we have taken a look at some basic questions of philosophy of science. One central idea in this philosophy of science is that we need to put our theoretical speculations to the test. In the next chapter, we will work on understanding how such tests work, and how to design them yourselves.