Human behaviour when it has to make a decision, tends to maximise their utility, and Adam Smith, the father of modern economics, explains that people can accomplish their aim when they act in their own self-interest, indeed, as F. Y. Edgeworth wrote in his “Mathematical Psychics: An Essay on the Application of Mathematics to the Moral Sciences”: ‘the first principle of economics is that every agent is actuated by self-interest’ (1881, p. 16). However, the self-interest can lead to negative consequences for the community and the society. This essay In the first case, according to a WWF report, people will no longer have the possibility to afford fish by 2050 due to overfishing, and this will lead to a collapse of the fish market and it will impact all the world, but especially the developing coastal countries. The problem here is not fish, but overfishing, which is a self-interest behaviour that damage the ecosystem, in fact fish are being caught too fast and the oceans are not quick enough to restore in time what was taken. Many people rely on fish for his nutritional value which includes high quality protein and vitamins like D and A, and from the latest research, it turned out that eating fish while pregnant have benefits in the development of the brain of unborn children. Knowing all these advantages derived from eating fish, the demand for it grew by 16.5 million tons in the last years and as the world population continue to grow, the request of seafood will keep increasing and according to experts it will rise by 20% by 2030 (Bloomberg, 2014). This increase, and the advanced technology of modern fishing ships are decimating more than 80% of the ocean predators like tuna and groupers and this is leading to a change in the market, in other words fishermen have to target smaller species, and with the addition of illegal fishing and other regulatory problems, the fish that is on the dish will no longer exist. This issue like I said before shows that self-interest leads to a serious habitat matter, because both parties, demand and supply want the most desirable option in their preferences, in this case for the demand, an increasing quantity of fish, and instead for the supply, a continuous increase of the demand, so the profit will rise and consequently, more and more advanced fishboats will be at sea, on that fact, experts believe that all the world’s equipment for fishing together is enough to fish on four planets like the Earth (eSchoolToday, 2016). All this will lead to a total catastrophe for human lives not only because of the numerous vessels but also for the industries, indeed, fishing boats release oil, liquid spills, chemical and solid elements into the water and all the industrial and nucleal waste end up in the ocean, and both are causing water pollution, which means contaminated fish, and for the countries that depend from seafood will be even more difficult because their economy will fall, but also fishermen and everyone who works in the fish industry will go out of business. Since fish is a common resource, people get to over use it and this can cause a long-term decline in maximum sustainable yield, this happens because people are acting in their personal interest without thinking at the consequences that there will be in the community (Riley, 2016), this is the tragedy of the commons theory, which assumes that people during the process of decision making, take the direction for maximise their own utility, but if everybody does the same, the demand will overwhelm the supply and the resource will become unavailable to some or all (Rouse, 2013). Mike Fincken of GreenPeace wrote a blogpost called “our oceans, our responsibility”, which means that people have to take care of the oceans for the sake of them and the future generations (Fincken, 2017), indeed president Bill Clinton said in a press announcement: “we know that when we protect our oceans we’re protecting our future.” Some conservation groups like WWF or the Nature Conservancy are already using some solutions to make the fishing industry more sustainable, as working with governments to prepare effective regulations and specific policy, or also helping developing countries. Instead, in the second case is discussed the problem of vaccination that is considered an effective way to safeguard people, especially kids, for someone, but it is also viewed as a negative healthcare for children by other people, and if an increasing number of people adopt this view, consequently, children will be more at risk of infections and this will cause a society-wide health crisis. Since vaccines were discovered, many lives were saved by infectious diseases like Hepatitis-B or Malaria, but either way they have some adverse effects. Every year, more than 2 million lives are saved by vaccines, but even if it is a great success, more than 3 million people die from vaccine-preventable diseases each year (Offit, 2014). This leads to a loss of confidence in vaccines, for example, a person called John Salamone found out that these antibiotics have real side effects on his son, even if they are really rare, indeed, when he gave to his son, David, the oral polio vaccine, he started to became weak, in other words, David contracted polio from the vaccine, “we basically gave him polio that day” said Salamone in an interview (Kwok, 2011). With the growth of these cases, people will not only lose faith in these medicines, but will also spread the idea of anti-vaccine misinformation, in fact many believe that vaccines might cause autism, for example they think that the measles-mumps-rubella can cause autism by damaging the intestinal lining or they suppose that the thimerosal, an ethylmercury-containing preservative in some vaccines, is toxic to the central nervous system (Plotkin, Gerber, Offit, 2009). But thanks to the studies and the research, it has been demonstrated that there is no connection between vaccines and autism, indeed, as Dr. Jeffrey S. Gerber and Dr. Paul A. Offit said in their book “Vaccines and Autism: A Tale of Shifting Hypotheses”, that twenty epidemiologic studies have shown that neither thimerosal nor MMR vaccine causes autism. These studies have been performed in several countries by many different investigators who have employed a multitude of epidemiologic and statistical methods (Plotkin, Gerber, Offit, 2009). Another obstacle of vaccination is the religion, in fact, the church may be really influential in the process of decision making of a rational agent, a concrete example is the Dutch Reformed Church that refuses vaccines because of their adverse effects and also because they think that vaccines interfere with the relationship with their god (Raptor, 2014), but due to this belief, in 2013, a Dutch reformed community in the Netherlands was hit by a measles outbreak, with 1226 reported cases (Cluskey, 2013). For a rational person choose to use vaccines is a decision under risk and uncertainty, that is why, doctors must do more tests to improve the safety of the medicine, so as to reduce serious and permanent risks and also identify high risk factors that can increase “individual susceptibility” to vaccine reactions, in other words, a person who is at risk to be infected by a disease. With these improvements and with the knowledge that vaccines are also money-saving, people will agree to vaccinate their children and themselves. The common problem between the two cases is that people make their decisions without thinking that they can affect a whole society, and even if they are driven by self-interest, this could lead them to the wrong direction. When looking at the two cases, it is possible to see that if every person act in their own self-interest, this may result into a complete disaster, like in the first case, the possible disappearance of marine life, and in the second case, the risk of an epidemic disease that could affect, especially, children. Citing a quote of Meir Soloveichik, “a society that is all self-interest and no comradeship is not a society at all. But a society that is all comradeship and no self-interest is also not a society”, people need to consider also the consequences of their decisions, which are always hidden by those benefits that people try to achieve through the maximisation of their utility, in other words they have to act for the common good. All Individual choices should be unrestricted. What is good for each individual at any given point should only be decided based on his or her interests. In my opinion, this statement argues that people when making decisions consider only their own utility by choosing the best option between their own preferences, without focusing on other people interests. By linking this statement to the two cases before, it can be seen that if people base their decisions only in their interests, this can lead to egoism, that could create conflicts between different interests, even if Thomas Hobbes, (1651) philosopher and one of the founders of modern political philosophy, justifies this saying in his book “no man giveth but with intention of good to himself; because gift is voluntary; and of all voluntary acts the object to every man is his own pleasure”, but conflicts can lead to the collapse of the society, that is why people should work together for a functioning society, in fact, Emile Durkheim, a French sociologist, regards that society is a functional organism, where each part plays an important role and they cannot function alone, and when one is wrong or fail, the other parts must solve this problem. A community is stable when people work for the well-being of the entire society, in other words, they have to make decisions, still base on their desires but with the understanding of influencing positively other people. The Social Norms Theory could solve these issues, because the aims of this theory are to understand the environment and interpersonal influences in order to change a person’s behaviour. Influences from friends, family or media are really important in order to direct the behaviour of young people in the right direction, indeed, to settle these kind of problems, as overfishing and vaccination, it has to begin with the new generations because they are the future, and these issues depend especially on adults, but everybody can change these situations.