Carl Sagan on Knowledge

"This is Phobos... Its mean density is known, and it is consistent with organic matter. Deimos... same story."

"Superstition is marked not by its pretension to a body of knowledge but by its method of seeking truth."

"It is important to distinguish between the amount of information and the quality of that information."

"For a long time the human instinct to understand was thwarted by facile religious explanations."

"The enterprise of knowledge is consistent surely with science; it should be with religion, and it is essential for the welfare of the human species."

"Can We Know the Universe? – 1979 essay by Carl Sagan, taken from his book Broca's Brain"

"The idea of science as a method rather than as a body of knowledge is not widely appreciated outside of science, or indeed in some corridors inside of science."

"The suppression of uncomfortable ideas may be common in religion and politics, but it is not the path to knowledge; it has no place in the endeavor of science."

"We have heard the rationales offered by the nuclear superpowers. We know who speaks for the nations. But who speaks for the human species? Who speaks for Earth?"

"Anything you don’t understand, Mr. Rankin, you attribute to God. God for you is where you sweep away all the mysteries of the world, all the challenges to our intelligence. You simply turn your mind off and say God did it."

"The search for patterns without critical analysis, and rigid skepticism without a search for patterns, are the antipodes of incomplete science. The effective pursuit of knowledge requires both functions."

"For all I know we may be visited by a different extraterrestrial civilization every second Tuesday, but there's no support for this appealing idea. The extraordinary claims are not supported by extraordinary evidence."

"The vast distances that separate the stars are providential. Beings and worlds are quarantined from one another. The quarantine is lifted only for those with sufficient self-knowledge and judgement to have safely traveled from star to star."

"The size and age of the Cosmos are beyond ordinary human understanding. Lost somewhere between immensity and eternity is our tiny planetary home. In a cosmic perspective, most human concerns seem insignificant, even petty. And yet our species is young and curious and brave and shows much promise. In the last few millennia we have made the most astonishing and unexpected discoveries about the Cosmos and our place within it, explorations that are exhilarating to consider. They remind us that humans have evolved to wonder, that understanding is a joy, that knowledge is prerequisite to survival. I believe our future depends powerfully on how well we understand this Cosmos in which we float like a mote of dust in the morning sky."

"All inquiries carry with them some element of risk. There is no guarantee that the universe will conform to our predispositions. But I do not see how we can deal with the universe—both the outside and the inside universe—without studying it. The best way to avoid abuses is for the populace in general to be scientifically literate, to understand the implications of such investigations. In exchange for freedom of inquiry, scientists are obliged to explain their work. If science is considered a closed priesthood, too difficult and arcane for the average person to understand, the dangers of abuse are greater. But if science is a topic of general interest and concern—if both its delights and its social consequences are discussed regularly and competently in the schools, the press, and at the dinner table—we have greatly improved our prospects for learning how the world really is and for improving both it and us."

"There are many hypotheses in science that are wrong. That's perfectly alright; it's the aperture to finding out what's right. Science is a self-correcting process. To be accepted, new ideas must survive the most rigorous standards of evidence and scrutiny. The worst aspect of the Velikovsky affair is not that many of his ideas were wrong or silly or in gross contradiction to the facts; rather, the worst aspect is that some scientists attempted to suppress Velikovsky's ideas. The suppression of uncomfortable ideas may be common in religion or in politics, but it is not the path to knowledge and there is no place for it in the endeavor of science. We do not know beforehand where fundamental insights will arise from about our mysterious and lovely solar system, and the history of our study of the solar system shows clearly that accepted and conventional ideas are often wrong and that fundamental insights can arise from the most unexpected sources."

"The Cosmos is all that is or ever was or ever will be. Our feeblest contemplations of the Cosmos stir us — there is a tingling in the spine, a catch in the voice, a faint sensation as if a distant memory, of falling from a height. We know we are approaching the greatest of mysteries."

"We on Earth have just awakened to the great oceans of space and time from which we have emerged. We are the legacy of 15 billion years of cosmic evolution. We have a choice: We can enhance life and come to know the universe that made us, or we can squander our 15 billion-year heritage in meaningless self-destruction. What happens in the first second of the next cosmic year depends on what we do, here and now, with our intelligence and our knowledge of the cosmos."

"Skepticism is the chastity of the intellect, and it is shameful to surrender it too soon or to the first comer; there is nobility in preserving it coolly and proudly through long youth, until at last, in the ripeness of instinct and discretion, it can be safely exchanged for fidelity and happiness."

"One of the saddest lessons of history is this: If we've been bamboozled long enough, we tend to reject any evidence of the bamboozle. We're no longer interested in finding out the truth. The bamboozle has captured us. It's simply too painful to acknowledge, even to ourselves, that we've been taken. Once you give a charlatan power over you, you almost never get it back."

"Those afraid of the universe as it really is, those who pretend to nonexistent knowledge and envision a Cosmos centered on human beings will prefer the fleeting comforts of superstition. They avoid rather than confront the world. But those with the courage to explore the weave and structure of the Cosmos, even where it differs profoundly from their wishes and prejudices, will penetrate its deepest mysteries."

"Humans may crave absolute certainty; they may aspire to it; they may pretend, as partisans of certain religions do, to have attained it. But the history of science — by far the most successful claim to knowledge accessible to humans — teaches that the most we can hope for is successive improvement in our understanding, learning from our mistakes, an asymptotic approach to the Universe, but with the proviso that absolute certainty will always elude us."

"The idea that a God or gods is necessary to effect one or more of these origins has been under repeated attack over the last few thousand years. Because we know something about phototropism and plant hormones, we can understand the opening of the morning glory independent of divine microintervention. It is the same for the entire skein of causality back to the origin of the universe. As we learn more and more about the universe, there seems less and less for God to do."

"If you know a thing only qualitatively, you know it no more than vaguely. If you know it quantitatively—grasping some numerical measure that distinguishes it from an infinite number of other possibilities—you are beginning to know it deeply. You comprehend some of its beauty and you gain access to its power in the understanding it provides. Being afraid of quantification is tantamount to disenfranchising yourself, giving up on one of the most potent prospects for understanding and changing the world."

"We've arranged a global civilization in which the most crucial elements — transportation, communications, and all other industries; agriculture, medicine, education, entertainment, protecting the environment; and even the key democratic institution of voting — profoundly depend on science and technology. We have also arranged things so that almost no one understands science and technology. This is a prescription for disaster. We might get away with it for a while, but sooner or later this combustible mixture of ignorance and power is going to blow up in our faces."

"Unlike the La Pérouse expedition the Conquistadors sought not knowledge but Gold. They used their superior weapons to loot and murder, in their madness they obliterated a civilisation. In the name of piety, in a mockery of their religion, the Spaniards utterly destroyed a society with an Art, Astronomy and Architecture the equal of anything in Europe. We revile the Conquistadors for their cruelty and shortsightedness, for choosing death. We admire La Pérouse and the Tlingit for their courage and wisdom, for choosing life. The choice is with us still, but the civilisation now in jeopardy is all humanity. As the ancient myth makers knew we're children equally of the earth and the sky. In our tenure on this planet we've accumulated dangerous evolutionary baggage, propensities for aggression and ritual, submission to leaders, hostility to outsiders, all of which puts our survival in some doubt. But we've also acquired compassion for others, love for our children, a desire to learn from history and experience and a great soaring passionate intelligence, the clear tools for our continued survival and prosperity. Which aspects of our nature will prevail is uncertain, particularly when our visions and prospects are bound to one small part of the small planet Earth. But up there in the Cosmos an inescapable perspective awaits. National boundaries are not evident when we view the Earth from space. Fanatical ethnic or religious or national identifications are a little difficult to support when we see our Earth as a fragile blue crescent fading to become an inconspicuous point of light against the bastion and the citadel of the stars. There are not yet obvious signs of extraterrestrial intelligence and this makes us wonder whether civilisations like ours rush inevitably headlong into self-destruction."

"I have a foreboding of an America in my children's or grandchildren's time -- when the United States is a service and information economy; when nearly all the manufacturing industries have slipped away to other countries; when awesome technological powers are in the hands of a very few, and no one representing the public interest can even grasp the issues; when the people have lost the ability to set their own agendas or knowledgeably question those in authority; when, clutching our crystals and nervously consulting our horoscopes, our critical faculties in decline, unable to distinguish between what feels good and what's true, we slide, almost without noticing, back into superstition and darkness."

"Proponents of doctrinal religions—ones in which a particular body of belief is prized and infidels scorned—will be threatened by the courageous pursuit of knowledge. We hear from such people that it may be dangerous to probe too deeply. Many people have inherited their religion like their eye color: they consider it not a thing to think very deeply about, and in any case beyond our control. But those with a set of beliefs they profess to feel deeply about, which they have selected without an unbiased sifting through the facts and the alternatives, will feel uncomfortably challenged by searching questions. Anger at queries about our beliefs is the body’s warning signal: here lies unexamined and probably dangerous doctrinal baggage."

"But our openness to the dazzling possibilities presented by modern science must be tempered by some hard-nosed skepticism. Many interesting possibilities simply turn out to be wrong. An openness to new possibilities and a willingness to ask hard questions are both required to advance our knowledge. And the asking of tough questions has an ancillary benefit: political and religious life in America, especially in the last decade and a half, has been marked by an excessive public credulity, an unwillingness to ask difficult questions, which has produced a demonstrable impairment in our national health. Consumer skepticism makes quality products. This may be why governments and churches and school systems do not exhibit unseemly zeal in encouraging critical thought. They know they themselves are vulnerable."