This doctoral thesis aims to better understand why and to what extent people invoke supernatural explanations when unpredictable negative life events (such as misfortunes, illnesses, and natural catastrophes) occur. Supernatural explanations are found in most (if not all) cultures around the world. Often, people do not solely call to supernatural explanations, as they are aware that some natural factors must also play a causal role in bringing about negative events. Research has also shown that supernatural thinking does not result from simply filling in a knowledge gap or from people's previous beliefs. This thesis investigates two psychological mechanisms that may explain how supernatural explanations come readily into mind: (1) a need for predictability, and (2) an intuitive understanding of causal links in terms of morality. Based on previous research, two main cognitive aspects are thought to underpin predictability: (1) certainty, i.e., whether information about natural causal factors is available or lacking, and (2) frequency, i.e., whether an event happens frequently or rarely. It is first hypothesized that supernatural explanations may serve a compensatory psychological function and be invoked when negative life events happen because they help restore our need for predictability when it is threatened, that is, when aspects of an event are uncertain or infrequent. However, supernatural explanations for misfortunes, illnesses, and natural catastrophes, often bear a moral component. Who has never thought whilst hearing about somebody's woe, "he did not deserve this, he is a good person" or conversely, "he had it coming"? The second hypothesis is that information about the moral status of people's previous actions (e.g., the action being morally wrong) triggers supernatural explanations (e.g., supernatural agents bring about negative events as punishment for people's wrongdoings) as a direct consequence of the way our evolved moral cognitive processes work, resulting in intuitive moral causation. Two experimental studies manipulating variables related to predictability and morality in the context of scenario research were implemented as an online questionnaire to test these hypotheses. Study 1 first tested the role of certainty (in the form of availability of information about the natural causes of an event) and the role of moral information (wrongdoing versus rightdoing versus no moral information) in triggering supernatural causal attributions. A secondary aim was to verify two dispositional tendencies related to the need for predictability: individuals' tendencies to be aversive to uncertainty on the Intolerance of Uncertainty Scale (IUS) and individuals' tendencies to detect illusory patterns in pictures containing random noise (snowy pictures). In the following studies, two measures of supernatural causal thinking were implemented and measured different psychological processes: (1) the qualitative measure, which assessed participants' explicit beliefs about the supernatural causation of an event, and (2) the quantitative measure, which assessed supernatural causal factors which crossed participants' minds while reading the vignette. Results of the first study showed that low certainty and information about wrongdoing significantly increased the frequency of supernatural explanations (i.e., qualitative measure) and of supernatural causal factors crossing participants' minds (i.e., quantitative measure). Also, participants having supernatural causal factors crossing their minds tended to score higher on the illusory pattern detection task and the Intolerance of Uncertainty Scale. The second experiment aimed at reproducing and expanding results from Study 1. In this experiment, the scenarios were modified to also test the second aspect of unpredictability (low frequency of events). Another addition was the inclusion of two levels of harm (low versus high) caused by the event, as harmful consequences of the event might be relevant in the motivation to provide an explanation. The results successfully replicated the role of wrongdoing (for both qualitative and quantitative measures) and uncertainty (solely quantitative measure) in triggering more supernatural causal thinking, but showed feeble evidence for the role of frequency. The role of intolerance of uncertainty (IUS) as a dispositional factor was also validated by the experimental results. The second experiment also further investigated what cognitive mechanisms could underpin supernatural moral causation when wrongdoing is perceived. Baumard and Chevallier (2012) proposed that attribution to immanent justice may result from our evolved sense of fairness which would trigger the perception of misfortune as a retribution when they seem proportionate. Accordingly, a follow-up measure probing participants' sense of the deservedness of the event was created to gauge this. The aim was to probe whether participants' supernatural causal thinking was elicited by perceiving the negative event in terms of harm in general (i.e., any kind of harm) or in terms of deserved harm (i.e., harm proportional to wrongdoing). Results of the study showed that supernatural causal thinking (qualitative and quantitative measures) was strongly related to the perception of misfortune as a deserved punishment. These results indicate that supernatural explanations tend to arise when the event received is perceived as fair harm rather than simply unwarranted harm. Finally, participants' sense of deservedness was significantly higher for individuals most intolerant to uncertainty. Together, these results suggest that the prevalence of supernatural explanations for events such as misfortune, illness and natural catastrophe results from intuitive evaluations of such events in terms of fairness, especially when one is averse to uncertainty. Two possible conclusions are discussed: either (1) supernatural causal thinking results from the misfiring of specific cognitive systems dedicated to our sense of fairness (i.e., false positive), or (2) supernatural explanations are a form of motivated reasoning that exploits our moral intuitions in order to reduce uncertainty and regain a sense of predictability on the world (i.e., which could potentially correspond to the cognitive mechanisms underlying Just-World Theory).