The Varieties of Scientific Experience: A Personal View of the Search for God
-- Carl Sagan
This is a compilation of lecture series given by Carl Sagan as Gifford Lectures (They were established to "promote and diffuse the study of Natural Theology in the widest sense of the term — in other words, the knowledge of God." The term natural theology as used by Gifford means theology supported by science and not dependent on the miracles. The lectures are given at the Scottish universities: University of St Andrews, University of Glasgow, University of Aberdeen and University of Edinburgh. - Wikipedia)
The lecture series is organized into 3 parts. First part deals with the origin of universe and how evolution of science has lead to the diminishing role of god, which also gave some death blows to human vanity. Switch from Geocentric to Heliocentric theory, made earth 'an earth' from 'the earth' and world we live in 'a world' among many probable worlds. The discussion around the origin and evolution of life (that took billions of years after the formation of earth) also answers some of the arguments put forth by the people, who believe that such complexity can't be arrived without an all powerful god. There was a nice back of the envelope calculation to understand the time that we took to reach this level - If our ancestors (father, father's father, his father... ) walk one behind another at ordinary human pace into a room, it takes one full week to see a creature that walks on all four legs. Now, it is rude, and we make only fools of ourselves, if we simply attribute such beautiful and complex evolution to some super-nature, with out appreciating the evidence of evolution.
The second part discusses the origin of life and presence and importance of organic matter. Author has extensively worked on projects related to extraterrestrial intelligence and an active member of SETI Institute (Search for Extra-Terrestrial Intelligence) that claims, "We believe we are conducting the most profound search in human history — to know our beginnings and our place among the stars". While calculating the probability of extra terrestrial life, he proposes a formula with multiple variables, among which one variable stands out. Average life of a technical civilization. How long a civilization, with 10 times more nuclear weapons than what is needed to destroy the entire civilization, survives ? Now, we don't have an estimate here. It could be anything. If all countries are sane enough, we may live really long. But, that variable has a lot to do with the chances of meeting or not meeting our friends on other planets (if there are any, and if they are advanced enough to contact us, won't they be stupid enough to destroy themselves ?)
The final part discusses the greatest delusion that humanity suffers from (the God), what a religion talks about our responsibility to get life on earth going, man's relentless struggle to find someone to worship, relation between religious experience and molecular influence on human mind and body, the statistical significances that we generally take for granted (the general rule in the universe is: extinction is the rule, survival is an exception) etc., He concludes with some stress on the importance of the current times that we live, where we see unprecedented changes and technological advancements, and why should we question everything and try to know the truth, with a courageous intent to figure out the reality without emotional predispositions.
And, finally, with utmost humility, he declares, absence of evidence is not evidence of absence and that's true with God as well. But, very important thing here that shouldn't be missed is, it is neither evidence of presence. The onus to provide evidence still lies with the believers.
Needless to say, one of the best books that I ever read.
