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An evidentialist can be extreme about epistemic requirements in a couple of different ways. At the reductionist end of the spectrum are those who think our epistemic obligations are fully satisfied by the mere having of evidential fit—where having implies nothing about doing. Your beliefs ought to align with your evidence, in other words, but there’s nothing you’re obligated to do in order to get yourself into the epistemically optimal position. At the expansionist end of the spectrum are those who think we ought to do more—epistemically-speaking—than just bring about a state of evidential fit. We ought to get more evidence, for instance, if it’s somehow relevant to our beliefs. Rather leery of extremists, Stapleford and McCain prefer a moderate account of epistemic obligation. It’s a conjunction of three theses: (1) We never have an epistemic duty to believe any particular proposition; (2) We’re epistemically obligated to reflect on our evidence in order to produce a state of evidential fit; (3) We’re never epistemically obligated to acquire any additional evidence. The aim of this chapter is to make these plausible.

Phenomenal conservatism as developed by some philosophers faces a previously unnoticed problem. The problem stems from the fact that, as some develop the view, phenomenal conservatism holds that seemings alone justify—sensations have no justificatory impact. Given this, phenomenal conservatism faces a problem analogous to the isolation objection to coherentism. As foundationalists, supporters of phenomenal conservatism will want to allow that the isolation objection is effective against coherentism, and yet claim that a similar objection is not effective against their view. Unfortunately, it appears that on most understandings of the nature of seemings phenomenal conservatism can only avoid its version of the isolation objection by sacrificing its internalist character.

Human evolution is a hotly debated topic despite the vast amount of evidence (anatomical, biochemical, DNA, fossil) about our ape origins. Worse than that, the uncertainties about the details of human evolution are often used to question the fact of human evolution. Therefore, it is important to explain why these uncertainties are not enough to blur the big picture. And even if we never come to know all the details of human evolution, this does not entail that we should not accept it as fact. The problems with this acceptance do not stem from a lack of scientific evidence in support of evolution, but rather from the perceived threat to some people’s worldviews.

A primary good of science is that it allows us to accurately predict what will happen in the future. Knowing what to expect helps alleviate anxiety about the future and allows for good planning. However, although scientific predictions are often very precise and accurate, they are inherently uncertain. In order for a scientific prediction to be certain, several conditions would have to be satisfied. First, it would have to be certain that the universe is deterministic, but this is contested by both philosophers and scientists. Second, it would have to be certain that the actual scientific laws governing the deterministic universe have been identified—this is far from certain. Third, the precise initial conditions that the prediction is drawn from would have to be known with certainty—it is impossible to know these with certainty. Nevertheless, despite the fact that scientific predictions are uncertain, it would be foolish to disregard them.

Genetic tests are becoming increasingly affordable; however, the way they are marketed might make people think that they can provide more answers than they actually can. There are many uncertainties involved. Even if we are sure that a person carries a particular DNA variant and that this variant is implicated in a particular disease—which for many variants is not entirely clear—there is not much that we can do with this information until the underlying biological mechanism is understood. It is only after understanding what problem is caused by the particular variant that specific recommendations can be made. However, the way genetic tests are usually marketed is not explicit about these uncertainties. On the contrary, it is often promised that such tests reveal information that is actually impossible to obtain.

Whereas we may think that knowledge requires certainty, this is not the case. We may be psychologically certain about something and still be wrong because of faults in our perception, because we are deceived, or because of reasoning errors. Epistemic certainty is impossible to achieve because we cannot be epistemically certain about anything. Fortunately, neither epistemic nor psychological certainty is a requirement for knowledge. Rather, what knowledge requires is good, solid evidence on the basis of which we can make choices and decisions. The better the evidence is, the better the choices and decisions can be. Thus, we can lead our lives successfully by relying on good evidence. We can certainly live with uncertainty.

People strive for certainty due to an inherent desire for it. Uncertainty seems to be stressful in the same unconscious manner as anger and fear. We cannot really control this feeling, and we feel relaxed only when we feel certain about what we know or about what we should anticipate. However, our world is filled with uncertainty and so are most aspects of our life. Therefore, instead for looking for certainty where it does not exist, we had better learn to appreciate uncertainty and learn to live and deal with it. Education could play a major role here. But a major shift is necessary from the current educational practice of providing yes or no answers to one that would educate people to understand and deal with risk and uncertainty.

Rather than being a detriment to science, uncertainty actually helps it advance. And understanding the role that uncertainty plays in science is extremely helpful for avoiding four serious dangers. First, appreciating uncertainty in science helps one to avoid being dogmatically certain. Good science is always open to revision in the face of new evidence. Second, appreciating uncertainty in science allows one to avoid the mistaken view that all theories and ideas are equally plausible. Third, since uncertainty is an inherent feature of science, appreciating its role helps one better understand science. Fourth, with a proper appreciation of uncertainty in science, it is much harder for one to be deceived about things like the link between tobacco smoke and cancer or the reality of climate change. In the end, uncertainty in science helps us to make the best decisions we can while encouraging us to continually seek new discoveries.

Contrary to what lay people may expect, uncertainty is inherent in science. Scientists admit that and recognize the difficulties in dealing with uncertainties inherent in the respective procedures. These uncertainties are a cause for concern and a motivation to improve these procedures; however, they are often mistakenly considered by lay people to devalue the respective scientific findings and conclusions. Climate change denialists, anti-vaxxers, and anti-evolutionists make this mistake, whereas uncertainties that arise in genetic testing and forensic science are often completely disregarded. However, these are all solid scientific domains despite limitations due to inherent uncertainties. The respective uncertainties can be expressed in the form of probabilities, and everyone needs to understand what these entail. However, it seems that people often misunderstand probabilities because of the way they are presented.

One of the chief aims of science is understanding. The primary way that we achieve understanding of natural phenomena is by constructing explanations of how and why the phenomena occur as they do. The explanations provided by science are inherently uncertain. Due to the complexity of the phenomena being explained and our limitations as humans, scientists rely on models when constructing explanations. By their vary nature, models are uncertain because they essentially involve idealizations (abstractions or distortions of the facts) for the purpose of simplification. Although scientists legitimately infer that the best explanation of a given phenomenon is true, this method of inference is always uncertain for at least two reasons. The first is simply that the data being explained are limited (i.e., there is always more data that could have been gathered). The second is that there are always alternative explanations that might later be discovered.

Understanding, rather than certainty, is the true aim of science. This is something that scientists and philosophers agree upon for good reasons. There are two main reasons for this. The first reason is that understanding is particularly valuable. It is widely acknowledged that understanding is a cognitive achievement that is even more valuable than knowledge. So, when aiming at understanding, science aims at an intellectual good that is very valuable. The second reason is that, as the aim of science, focusing on understanding instead of certainty provides a solid account of the success of science. If certainty were the aim of science, then science has not been very successful since it never achieves certainty. However, science has continually achieved deeper understanding of natural phenomena, so if understanding is the aim, science has been tremendously successful.

There is a general impression, enhanced by many TV shows, that forensic analyses are objective and infallible. Yet this is far from true. There are many reasons for this. Forensic analyses are not only limited by the quality and the quantity of the DNA analyzed, but also by mistakes that can be made during the interpretation of the findings. There are many uncertainties inherent in the respective procedures, and these must be carefully considered before a conclusion is drawn. Whereas forensic DNA analyses can really be informative, they have to be judged against other types of evidence. Most importantly, all these have to be carefully considered before a juridical decision is made all while making efforts to limit biases that might interfere.

Whereas there is broad agreement among most climate scientists that climate change is occurring and that it is mostly due to human activities, many people doubt this. There are several reasons for this. One is that, despite the solid evidence for climate change, uncertainties remain about its exact pace and mechanisms. Scientists may debate these issues among themselves, and this debate might be perceived as a lack of consensus among them even though this is not at all the case. Furthermore, the public representation of this topic often fails to show that the vast majority of climate scientists agree that climate change is happening because of what we humans do. At the same time, uncertainties remain, and so the predictions of scientists have limitations. What is necessary is for scientists to clearly communicate the evidence and explain that uncertainties may blur the details but not the big picture.

Scientists are experts in their respective domains because they have the knowledge, credentials, experience, and affirmation of their peers. They are, therefore, the experts when it comes to scientific matters. But individual scientists cannot know everything. Consequently, what matters is not the views of individual scientists but the collective and consensus view of the scientific community. However, the public is divided on the issue of whether to trust science and scientists. Polls in the United States show that scientists are relatively highly respected compared to other professionals, but, at the same time, about half of the people only have some trust in scientists. Worse than that, political orientation rather than science knowledge seems to have a major impact on attitudes toward science. Finally, even though there is a consensus view among scientists on topics like climate change, the public perception is that scientists are divided on such issues.

Whereas vaccines have helped save millions of lives over the past several decades, today there is a significant anti-vaccination (anti-vaxx) movement, especially in the United States, that questions their safety. The problem is that these anti-vaxx arguments focus on rare cases of side effects or—even worse—on unfounded connections between the administration of vaccines and particular conditions such as autism. Such reactions make people overlook the fact that several diseases that in the past killed millions of people have been completely or almost completely eradicated thanks to vaccines. Even though vaccine side effects are a real possibility, one has to weigh the risk of facing those (which is very low and arise in relatively rare cases) against the hundreds or thousands of children who, thanks to the vaccine, will avoid hospitalization or even death. Uncertainties always exist, and we cannot be absolutely certain about the efficacy and safety of any vaccine. But for many of them, there is solid evidence that the problems are rare, and certainly the affected individuals are a lot fewer than those who might suffer and even die from the disease.

At times people seem to have a mythical view of science as an infallible source of absolute certainty. Despite the prevalence of such a view, it is deeply misguided. All science is inherently uncertain. Two key factors that contribute to science’s inherent uncertainty are the complexity of natural phenomena and human limitations. Although the challenges posed by these two factors can be somewhat mitigated by way of scientific methods of investigation and the use of precise mathematical formulations, neither can be fully done away with. As a result, all science, no matter how precise or careful the methods it employs, is inherently uncertain. This is important to realize not only for truly understanding the nature of science, but also for appreciating that pointing out uncertainties that exist in domains like climate science, evolution, and vaccination in no way undercuts their claims to being legitimate, trustworthy science.

The findings of scientific research should be considered with caution both because there are uncertainties inherent in the respective procedures and because scientists can be subjective in their conclusions—and sometimes they can even be biased. Indeed, fraud and misconduct can be found in science, and this is a cause for concern. Nevertheless, this does not affect the overall value of scientific research. Science has strong foundations exactly because scientists are aware of these kinds of problems and do a lot to address them. One important criterion of the value of scientific research is its reproducibility; that is, the ability to use the same methods that other researchers have previously used and arrive at the same results. However, the rates of reproducibility (when they are available) indicate that it is relatively low. At the same time, scientists seem to face a “publish-or-perish” situation, even while retractions of published papers have increased. These are all reasons for concern. However, it is precisely the fact that scientist are aware of these issues that makes science trustworthy. The issue is not if science has flaws, but that its self-correcting nature can provide the means to deal with them.

Scientific knowledge is the most solid and robust kind of knowledge that humans have because of its inherent self-correcting character. Nevertheless, anti-evolutionists, climate denialists, and anti-vaxxers, among others, question some of the best-established scientific findings, making claims unsupported by empirical evidence. A common aspect of these claims is reference to the uncertainties of science concerning evolution, climate change, vaccination, and so on. This is inaccurate: whereas the broad picture is clear, there will always exist uncertainties about the details of the respective phenomena. This book shows that uncertainty is an inherent feature of science that does not devalue it. In contrast, uncertainty advances science because it motivates further research. This is the first book on this topic that draws on philosophy of science to explain what uncertainty in science is and how it makes science advance. It contrasts evolution, climate change, and vaccination, where the uncertainties are exaggerated, and genetic testing and forensic science, where the uncertainties are usually overlooked. The goal is to discuss the scientific, psychological, and philosophical aspects of uncertainty in order to explain what it really is, what kinds of problems it actually poses, and why in the end it makes science advance. Contrary to public representations of scientific findings and conclusions that produce an intuitive but distorted view of science as certain, people need to understand and learn to live with uncertainty in science. This book is intended for anyone who wants to get a clear view of the nature of science.

Science is in the business of explaining things. This is because scientific understanding of the world comes to by way of explanations. Science explains why sugar dissolves in water, why unsuspended objects fall, why the planets move like they do, and so on. Explanation is one of the primary aims of science. An explanation is a set of claims/information about dependence relations that exist between the explanandum and the explanans. There is an obvious sense in which explanations generate scientific knowledge. At the beginning of the nineteenth century, it was discovered that the orbit of Uranus, one of the seven planets known at the time, departed from the orbit as predicted on the basis of Isaac Newton’s theory of universal gravitation and the auxiliary assumption that there were no further planets in the solar system. One possible explanation was, of course, that Newton’s theory is false.