Letters from an Astrophysicist

by Neil deGrasse Tyson

The Carl Sagan dictum “extraordinary claims require extraordinary evidence” remains a potent guide when investigating the natural world for its underlying order. But it comes with a recurring risk: knowing enough about a subject to think you are right, but not enough about the subject to know you are wrong.

When I am asked what was around before the Big Bang, I say, “We do not yet know.” Often the reply is, “It must be something—it was surely God.” To go from “We don’t know” to “It must be God” is another example of an argument from ignorance. This kind of disconnect has no place in rational investigations, yet it perennially permeates the thoughts and statements of people who already know what they want to believe.

The most enduring thing about being human is the discovery of cosmic truths that transcend culture, politics, religion, and time, forming the corpus of knowledge and wisdom that we call civilization.

The theory of evolution is not something to “believe in.” Science follows evidence. And when strong evidence supports an idea, the concept of belief, when invoked the way religious people use the word, is unnecessary. In other words, established science is not an ensemble of beliefs, it’s a system of ideas supported by verifiable evidence.

I think often about what would constitute evidence for God. How about if, after adjusting for income and access to health care, pious people all lived longer than non-pious people? How about when a plane crashes, only the pious people survive? How about Jesus comes when people say he will come? (His second coming has been predicted by Christians for hundreds of occasions that have already passed, spanning the last 2000 years.) How about people pray for peace, and then all wars in the world stop permanently? How about good things happen exclusively to good people and bad things happen exclusively to bad people? How about an earthquake strikes Portugal on All Saints Day, while everyone is in Church, as it did in 1755, and it kills only people who are not in Church, rather than the tens of thousands of people who were, as what actually happened that fateful morning. These events would trigger serious (scientific) conversation about the existence of God and how he treats people who worship him versus those who do not.

If faith is a personal construct, then there can be no agreed-upon book of answers.

So while I will not declare that science can currently answer all questions, the trend is quite impressive, especially when compared with religion, which spent most of its history explaining things (answering whole categories of questions) via divine forces that, in fact, had natural explanations, such as disease, hurricanes, planetary orbits, etc.

I never think much about “why.” Why implies purpose set by external forces. I have always felt that purpose is not defined outside of ourselves, but from deep within.

On my deathbed, one thought I will surely have comes from the evolutionary biologist Richard Dawkins. He notes that we who die are the lucky ones. Most people—most genetic combinations of who could ever exist—will never be born, and so will never have the opportunity to die.

When you assess all the parts and functions of the body, we should be amazed that human physiology works at all. So when parts fail, as they will for all of us at some point, or even when tragedy strikes, as in your lost friends in the Corps, not enough of us reflect on how amazing it was to have been alive in the first place. Consider further that the Homo sapiens genome is capable of generating trillions of unique humans, which means most people who could ever exist will never even be born. So death is a kind of privilege of those few of us who have known life.

I teach my children about all the world’s major religions. Not pejoratively but anthropologically, which is, I think, a sensible way to broach comparative religion. In this way, they know that while there are multiple belief systems in the world regarding God and gods, there is only one science, and that science is the same no matter your birthplace, on Earth or anywhere else in the cosmos.

I do not know whether God is real. I simply know that the people who cite evidence in favor of God have overlooked the preponderance of evidence against it. Other widespread and timeless activities of human societies include war and infidelity and power struggles and slavery and exploitation. Just because something endures within and across cultures does not mean it is good or correct or the right thing to do for the future.

As for the urge to believe in an afterlife, note that for most of the history of life on Earth you did not exist. A condition that continued right up until your birth. That is not a hard thought to consider. Nor is it depressing. You simply had no existence or awareness of anything at all. It should therefor...

So therein lies a non-convergent point of our conversation: You already know where you want to land. And God is there to design it. I have no idea where I am going to land. And if there is a God of unwavering intelligence, this fact is simply not evident in the book of nature to the unbiased observer. Natural selection never claims perfect design, or even good design, only a design that is more effective than that of a competing species, allowing survival long enough to reproduce. Nothing else matters to the process. Further, I never said the universe was not designed. I simply said that if it was designed, then there is ample (and widely ignored) evidence to demonstrate the designer’s blunders right alongside all those things that are marvelous.

Often people, especially religious people, look outside themselves to find the meaning of life—in scripture, in messages from religious leaders, religious relics, and so forth. When you do this, and do it for your entire life, it becomes hard to imagine life without this kind of spiritual structure constructed for you and around you. But suppose you instead looked within yourself? By doing so, it’s not hard to find meaning in life by doing meaningful things—caring for others less fortunate than you, raising children, accomplishing hard tasks that give you physical, intellectual, or emotional fulfillment. The drive to do this, without any reference to religious texts at all, can be quite fulfilling.

Finally, deeply religious people sometimes ask, “Without God, why should people be civil to one another?” or “What’s to stop people from committing crimes or even murder in the absence of divine judgment?” There is a simple answer to this: prison. That’s why laws exist, to restrain offensive behavior from person to person and between person and property. This recipe works for most people. In fact, in Europe, there are whole countries (e.g. Switzerland, The Netherlands, England, France, Sweden) where religion plays hardly any role in politics, culture, business, or family, yet they enjoy far lower rates of violent crime than in America, where more than 9 in 10 people say they are religious. In these other countries, the fraction of people who say they are religious is typically less than 1 in 10.

There is a growing anti-intellectual strain in this country that may be the beginning of the end of our informed democracy. Of course, in a free society you can and should think whatever you want. And if you want to think the world is flat go right ahead. But if you think the world is flat and you have influence over others, then being wrong becomes being harmful to the health, the wealth, and the security of our citizenry.