Lots of people feel that Optimism is positive and Pessimism is negative. They believe that every one should be optimistic. Optimists believe that people should not worry about their future or the future of their children but just enjoy the present. The Author believes that Optimists are a dangerous breed. Ronald Regan, an optimist, believed that financial institutions were best regulated by market forces and dismantled the regulatory mechanism established by the United States’ Administration to monitor the activities of banks and other financial institutions after the Great Depression. His optimistic deregulation of the banks and financial institutions enabled corporate greed to create the Sub Prime Mortgage Bubble that burst in 2007-2008 causing the global financial meltdown and brought Capitalism into crisis. The Optimists in the British Petroleum management tried to save a few million dollars in cost by not using a remote controlled blowout preventer while drilling for oil in the Gulf of Mexico and caused one of the worst drilling and ecological disasters in the history of oil production. The Optimists in the Tokyo Electric Company, to save costs, allowed its nuclear reactors at Fukushima Daiichi Nuclear Power Plant to be designed to withstand an earthquake of 7 on the Richter scale even though Japan is located in a seismically active zone where earthquakes of strength 9 and above have occurred earlier. The plant was not designed to resist tsunamis. The life of reactor number 1, which was forty years old, was extended by 10 years without due diligence. So, when an earthquake of 9 on the Richter scale and tsunami hit Japan on March 11, 2011, the nuclear power plant was severely damaged and resulted in the second most disastrous situation at a nuclear power plant in the world. Instances of disasters caused by decisions of optimists are endless. Dangers posed by Optimism need to be exposed so that the world becomes a less dangerous place to live in.The Rational Pessimists, contrary to popular belief, are not alarmists. They do not believe that the world is coming to an end or that the standard of living of all the people of the world is going down. They do not believe that the United States and Europe, though in terminal decline as economic powers, are going to disappear from the face of the earth. They believe that most innovations and developments in science and technology are beneficial to mankind. They are ready to concede that we have made great strides in science and technologies and will continue to make progress and achieve new landmarks.The Rational Pessimist is actually a realist. He is aware of the dangers that lurk in this world and take reasonable precautions. Rational pessimism stems from two fundamental truths. The first fundamental truth is that in spite of all the progress we have made in science and technology, man is powerless in the face of the fury of nature. It has no answer to earthquakes, tsunamis, floods, hurricanes, volcanic eruptions and droughts which periodically ravage the earth bringing death and destruction in its wake.The other fundamental truth is that in spite of all the progress in science and technology and the increased prosperity that it has brought, human nature has changed for the worse. Satanic traits like greed, arrogance, cruelty, intolerance, lust, deceit, selfishness have spread like wildfire while Godly traits like compassion, honesty, humility, tolerance, forgiveness, charity, fidelity, prudence and a willingness to share is declining day by day.This book seeks to highlight the reasons on which “Rational Pessimism” is based.This book also seeks to make the readers “Rational Pessimists” who hope for the best but prepare for the worst.