Does Philosophical Materialism Tend to Indirectly Increase Global Warming?

There are two definitions of the word “materialism.” One refers to a lifestyle emphasis, and the other refers to a philosophical position. Materialism as a lifestyle emphasis means centering your life around the acquisition and enjoyment of material things. A person pursuing a materialistic lifestyle may organize his life around getting a bigger house, getting a bigger or faster car, buying fancy clothes and gadgets, and so forth.

A person's carbon footprint is the amount of carbon dioxide emitted as the result of a person's consumption activities. Assuming that what we are told is correct (that increased carbon footprints tend to increase global warming), it is rather clear that lifestyle materialism tends to increase global warming. If a person thinks that “happily ever after” means a 2000-square-foot home and two big gas-guzzling cars, along with frequent trips to luxury hotels in distant cities, he may well have a carbon footprint much greater than if he put little value on such things.

Philosophical materialism is something quite different from lifestyle materialism. Philosophical materialism is the position that matter (or mass-energy) is all that exists (with the possible exception of blind impersonal forces such as gravitation, or laws of nature). Not believing in any type of deity, spirits or souls, a philosophical materialist thinks that this earthly life is the only life a human will ever have, and that no one will have an afterlife.

You might think that whether a person is a philosophical materialist has no relevance to global warming. But this may not be true. There is a reason for thinking that philosophical materialists may be more likely to have higher carbon footprints, and do more of the activities that increase global warming. The reason has nothing to do with the philosophical materialist's lack of belief in a deity. The reason has to do with the philosophical materialist's lack of belief in an afterlife.

Let us imagine two people, one named Joe and another named Jane. Joe is a hard-boiled philosophical materialist. He believes that this earthly life is the only life he will ever live. But Jane believes rather vaguely in some type of afterlife. She thinks that when she dies she may continue to live on in some type of heaven. She also thinks that perhaps she will be reincarnated, and come back to our planet to live another life.

Joe's attitude is summarized by slogans such as “you only live once.” Believing that he will have no afterlife, Joe thinks that this earthly life is his only chance to see the world's wonders and enjoy various types of pleasure. So Joe may create in his mind a “bucket list” consisting of a list of items he wants to do before he “kicks the bucket.” These may be items like this:

1. See the view from the Eiffel Tower.
2. Walk on the Great Wall of China
3. Take a glass-bottom boat tour in the Great Barrier Reef
4. Climb to the top of the Uluru rock in Australia
5. Swim in some beautiful lagoon in Tahiti

A "bucket list" of places to see before you die

Doing all of these things and other items on Joe's “bucket list” will add to global warming. That's because Joe will have to buy lots of jet plane tickets, and jet planes dump lots of carbon dioxide high into the atmosphere. But Joe justifies this by saying to himself, “This is the only chance I'll ever get to see such things.”

Joe may also buy himself a big home with a high carbon footprint, reasoning, “This is the only chance I'll ever get to live well.” And he may buy himself some gas-guzzling car or recreational vehicle, reasoning, “This is the only chance I'll ever get to drive well,” or “This is the only chance I'll ever get to see the whole USA.” With such reasoning, Joe's carbon footprint gets higher and higher.

But now let us consider Jane. Jane does not assume that her pleasures will be limited to the pleasures she gets during her earthly life. Jane thinks she will have some kind of afterlife, and that such an afterlife may offer unlimited opportunities for different kinds of pleasure. Thinking that she may find herself in some magnificent heavenly realm that totally surpasses the splendor of the home of the richest billionaire, Jane doesn't think along the lines of, “This is the only chance I'll ever have to live in grand style.” Jane thinks that perhaps as a disembodied spirit she may be able to move around to any place on the planet she wants to go, or that perhaps she will be reincarnated and have additional opportunities for physical earthly experiences. So she doesn't engage in thinking along the lines of, “This earthly life is my one chance to see the Great Wall of China.”

When it comes to eating habits, there may also be a difference between Jane and Joe. Jane may believe or suspect that all animals have souls, and this may cause her to limit her meat eating or may cause her to become a vegetarian. Jane may reason that raising pigs and cows for food may cause suffering for animals with souls, and that we should therefore not eat such animals. But not believing in any types of souls, Joe may eat lots of meat. In fact, when he comes to a restaurant, Joe's attitude of “this life is my only chance for pleasure” may cause him to try some meat dish he has never tried before. This is relevant to global warming, because the raising of animals for meat is one of the biggest contributors to global warming.

Now, who is more likely to have a higher carbon footprint, Jane or Joe? It seems that Joe will be much more likely to have a higher carbon footprint. Joe's thinking may well lead him to engage in activities that increase global warming. But Jane's thinking may make her less likely to engage in a high-carbon-footprint lifestyle.

It is certainly true that we can imagine a rather austere philosophical materialist whose carbon footprint is low. The main driver of a high-carbon lifestyle is not any philosophical position but a consumerist culture which is constantly sending us silly messages implying that your success in life is proportional to the size of your house, the size or cost of your car, and the distance you travel in jet planes. But by encouraging the thinking that this earthly life is our only chance for satisfaction, philosophical materialism does nothing to put a check on such a consumerist culture. So compared to rival assumptions, philosophical materialism does a bad job at discouraging the high consumption that worsens global warming. Although philosophical materialism does not necessitate lifestyle materialism, philosophical materialism may tend to encourage lifestyle materialism, which tends to increase global warming.

The armchair considerations here don't prove anything, but a systematic scientific study could shed further light on such a topic. I suggest this as a topic for a scientific researcher looking for a topic for a scientific paper. I can imagine such a study being done at low cost. You simply submit question lists to a wide variety of age groups and income levels, asking people both about their philosophical and religious beliefs and also about their consumption practices and carbon footprints. Then you look to see whether there is any correlation between the two.

Will Complex Code Cause Our Collapse?

Our complex society increasingly depends on computer software code, and that code is growing ever more complex and unmanageable. It is already very common in large companies for there to exist large software systems that no single person understands very well. When you have a large software system with more than 100,000 lines of code, it will often be that one person knows certain aspects of the software system, and someone else knows other parts of it; but there is no person who understands the full system very well.

As demand for software functionality grows, software engineers sometimes resort to using code generators. These are software tools that can quickly generate many lines of code. But such code is often very hard to understand. By using a code generator, a software developer may quickly add 10,000 lines of new code to a software system. But he may not understand such code. A rough rule of thumb among programmers is: if I didn't write the code, I don't understand it.

Many advanced computer programs use what are called neural networks or deep learning. When such code is used, the software ends up being pretty incomprehensible to humans. Software decisions end up being driven by extremely complex data, often data that is distributed across many different layers. In complex cases of such implementations, the computer itself doesn't understand how the data determines the decision, and neither does a human. It's what programmers call a “black box.”

There is a strong possibility of a future complexity crisis in which humans find they have created software systems of unfathomable intricacy that they can no longer understand. We can imagine a certain level of complexity – call it Complexity Level 10 -- that is the most complex level that any human can understand. It is all too possible that humans might build their way up to Complexity Level 11 or Complexity Level 12 or some higher level. There would then be a possibility of an “overshoot and collapse” situation, in which computer systems around the world start to break down because they have become too complex for anyone to understand, maintain or fix.

You don't have to have lots of bugs for a complex system to fail. A space probe to Mars failed because of a single line of errant software code. In a case like that, it wasn't good enough that 99.999% of the code worked right.

On May 6, 2010 there occurred an event called the Flash Crash, in which the stock market underwent a trillion-dollar dip, dropping by 900 points at 2:32 PM. By the end of the day, the market had largely recovered. The dramatic dip of the Flash Crash was apparently caused by program trading, in which investment portfolios are controlled by extremely complicated computer programs. No one is exactly sure why the Flash Crash occurred. It seems to be an example of complex computer programs acting in an unpredictable manner. We can only wonder whether some future version of the Flash Crash may bring down the financial system, or perhaps the electrical grid.

Some people are not worried about such a possibility, because they think that super-intelligent computers will fill in the gap. The idea can be stated like this:

Sure, software code will become too complex for humans to understand; but that's no problem because our ever-more-brilliant computers will be able to understand that code. Our computers will probably take over the job of writing and maintaining their own software, freeing us humans from such burdens.

But I believe we should reject the idea that computers will become smart enough to understand their own software code. Computers process information, crunch numbers, and process information. But they do not currently understand a single thing. A computer may be able to tell us instantly when Abraham Lincoln was born, but no computer has any real understanding of what a birth is, what a day is, what a human is, or who Abraham Lincoln was. There is no reason to think that any future advances will somehow give computers the understanding they now lack. A computer that does not understand anything will not suddenly be able to understand a little bit if we add some more lines of software code or some more chips or processors. Thinking that a computer will one day have understanding once you add faster processors or more lines of code to its software seems to be like thinking that one day when you get a much better TV, you'll be able to have a child fathered by your favorite TV character.

It seems, then, that we will not be saved from a software complexity crisis by computers that understand software code that has progressed beyond human understanding. A software complexity crisis will be worsened by short-sighted programming managers who demand more and more features be added to software, regardless of how this makes the code more and more difficult to maintain. We can compare such figures to real estate developers who keep yelling, “Higher, higher, higher!” to their architects, without worrying about buildings in danger of collapse because they are built too high.

The risks from such a software complexity crisis are great. Imagine it is the year 2030, and you are a typical computer programmer. Computer systems around the world may be undergoing more and more breakdowns, and your job is to fix one of them. You take a look at the software code, and see before you an ocean of unfathomable intricacy, perhaps a million lines of hard-to-read code. You ask yourself: how on earth did something like this ever come into existence? It's like the tangled jungle of complexity that is the US Tax Code, but much worse. After looking at just a little of the software, you feel like some ordinary person reading a 50-page scientific paper on quantum mechanics. You know your choice: either admit to your boss that you are hopelessly over your head, or cross your fingers and try to make some “blind fix,” rather like a layman walking into a nuclear power plant, and trying to fix rising core temperatures by fiddling with some of the dials. 

The agony of code too complex for you to understand

Then imagine such a situation happening in 10,000 different offices, to 50,000 “over their head” programmers, and you have a taste of the software complexity crisis that may lie ahead. I mentioned the possibility of the financial system or the power grid failing because of such a crisis. Another possibility is that we may upgrade nuclear weapon systems so that they are centered around computer systems that become way too complex to maintain or understand. A single fault in such a system might cause a nuclear war. The movie Fail Safe depicted such a thing when a small electronic unit failed, but the same thing might happen because of a single errant line of software code. Will some nuclear holocaust one day occur because of some computer code that grew too complex to be manageable?

Our Brains Have Nothing Like These 7 Things a Computer Uses to Store and Retrieve Data

It is commonly believed that when you recall something you are retrieving something stored in your brain. But none of our experiences suggest such a thing. When I retrieve an apple from my table using my hand, my body sends me two clear signals that my hand is doing the retrieval. The first is the touch sensation of my hand grasping the apple, and the second is the visual sensation of the apple in my hand. But when I retrieve a memory, my body does absolutely nothing to suggest to me that I am extracting this memory from my brain.

But our neuroscientists like to claim that our memories are stored in our brain. There is a way to test this claim. I will review each of the things that a computer uses to store and retrieve data, and in each case I will ask: is there something like that in the brain? I will use pretty much the simplest example of data storage and retrieval I can think of: the storage of a small file containing a few words of text. Below are the things that a computer uses to store and retrieve such information.

Item # 1: An Operating System

Besides applications that do specific things, a computer has what is called an operating system that does various low-level tasks. Bill Gates originally made his fortune by selling the MS-DOS operating system that was the first high-selling operating system used by personal computers. Nowadays if you have a desktop computer you may be using some Windows operating system such as Windows 10, or some Apple operating system. An operating system is a highly complex and coordinated base of code that serves as a kind of foundation for applications that are built to leverage that operating system.

As far as we know, the brain has no such thing as an operating system. There are particular genes that list the amino acid constituents of particular brain proteins, but those structural proteins are like hardware, rather than the software that is an operating system.

Item # 2: An Application to Store and Retrieve Data

While it is possible to store a small amount of data on a computer merely using a nerdy command-line string of characters, almost no one does that to store text data. Instead, 99% of the time someone will use an application to store data. An application is a program that does some specific type of work, typically by leveraging the functionality in the operating system. A person using a Windows operating system might use an application program such as Notepad, Wordpad, or Microsoft Word to store text data.

As far as we know, the brain has no such thing as application programs. No one has ever given a coherent description of how storing information to the brain would involve making use of “how to” instructions stored elsewhere in the brain, some set of instructions that could be compared to an application program.

Item # 3: The ASCII code for Encoding Information

Text is never directly written to a file stored on your computer's hard drive or a zip-drive. If, for example, you were to break apart your computer's hard drive (or break apart a small zip drive), and look at its contents in a high-magnification microscope, you would never see little tiny “a,” “b,” and “c” characters. What actually happens when your text data is stored is this: (1) the ASCII code is used to convert each of your text characters into a number; (b) those numbers are then converted from decimal into binary; (c) the binary information is then stored on your computer's hard drive or a zip drive. The ASCII code consists of a table in which each character is represented by a number.

Does the brain have anything like this? As far as we know, it does not. The ASCII code is an example of an encoding protocol, and no one has ever been able to discover any encoding protocol used by the brain to store information.

Item # 4: A Decimal to Binary Conversion Table or Utility

The ASCII code merely converts letter to decimal numbers, numbers that use the Base 10 system. But computers store information using binary code, and when binary is used, numbers are stored using the Base 2 system. So rather than directly writing text represented in the ASCII code, an application must convert from decimal to binary.

This is another encoding protocol that does not correspond to any functionality known to exist in the brain.

Item # 5: A Medium That Allows a Permanent, Stable Storage of Information

When a computer has all the bits needed to write, it must have a stable medium to write to. Some of the earliest stable media to write to were clay (used in writing cuneiform), parchment, and paper. Nowadays computers use a stable medium such as magnetic disks.

Does the brain have anything like this – some medium allowing a permanent, stable storage of information? It would seem not, at least nothing that could be used by the brain to store memories that last for years. The main assumption during the past decades has been that memories are stored in synapses. But synapses are an unstable “shifting sands” type of medium subject to high molecular turnover and structural turnover. As discussed in detail here, rapid molecular turnover in synapses should make them unsuitable for storing memories that last longer than a year. But humans are able to remember many memories for 50 years or longer. As a scientific paper puts it:

Experience-dependent behavioral memories can last a lifetime, whereas even a long-lived protein or mRNA molecule has a half-life of around 24 hrs. Thus, the constituent molecules that subserve the maintenance of a memory will have completely turned over, i.e. have been broken down and resynthesized, over the course of about 1 week. 

The DNA inside neurons is a stable medium for permanent information storage, but it doesn't seem to be used for storing our memories. Our DNA has been exhaustively studied by projects such as the Human Genome Project and the Encode project. No one has discovered the memories of any particular human in that human's DNA.

Shockingly, there seems to be no plausible candidate for a particular component in the brain where the brain could be storing memories that last for decades. Neither synapses nor DNA is such a plausible candidate.

Item # 6: A Storage Location System by Which the Exact Position of a Data Item Can be Specified, Allowing Fast Retrieval from an Exact Location

When a computer stores data on a hard drive or zip file, it's not similar to adding to a heap, something similar to pouring another cup of water in a swimming pool full of water. It's always rather like putting some new papers in a particular file of a filing cabinet. This is so that information can be retrieved rapidly. You can get papers from a file in a file cabinet quickly, but it would take you way too long to get that information if you just had some giant heap of papers in the middle of your office.

So whenever your computer stores data, it has some idea of a specific location where this data will be saved. For example, you may store your little text data in a file called SaturdayNote.txt in a folder or directory called MyTextFiles. That gives the computer a way to retrieve this information quickly, by first going to that particular folder or directory, and then searching for the file named SaturdayNote.txt file in that particular folder or directory.

Does the brain have any type of similar system for storing information in specific named locations? As far as we know, it does not. It's hard to conceive of how such a thing could possibly exist in the brain. The brain is more like a tower-sized ball of tangled spaghetti than some city with labeled streets. There seems to be no way in which a brain could ever know exactly where some data was that it was storing. Neurons don't have any coordinate system allowing anything to tell a precise location in the brain.  If your brain somehow wrote some information to a brain position of X=2345, Y=24342, Z=73252, there would be no way for the brain to record that exact position in a way that would allow that exact location to be quickly accessed. Writing some information to the brain would seem to be like writing on some index card, and throwing it into the middle of an Olympic-sized swimming pool full to the brim with index cards.  Under such a setup, instantaneous retrieval of some precise information should be impossible.

Item 7: Read/Write Functionality Allowing Data to Be Written to a Specific Location and Also Read From the Same Location

The discussion under Item #6 above was purely a discussion of an organizational system in which some data can be given a location for it to be stored. A separate requirement is that data can be written to a storage medium, and also read from that storage medium. The reading and the writing must occur in a very consistent way, so that the data read is exactly the same as the data written.

Your computer has one or more systems capable of such read/write functionality. For example, a hard disk in a computer is a read-write device. Below is a photo showing some of the rather complicated hardware involved. There is a a read-write arm which can move back and forth in a particular line, and also a spinning disk underneath that arm. At the end of the read-write arm is a read-write head that can read data when it is above some particular location. With the combination of these two things, the system can read and write from any desired location on the disk. 

Does the brain have any such read-write functionality? Some think that what is called long-term potentiation acts like a write system for storing memories. But the term long-term potentiation is very misleading. Long-term potentiation (LTP) is actually a very short-lived effect, almost always lasting less than a few weeks. The brain may have some kind of system for writing something that will last a short time, rather comparable to someone writing in the wet beach sand with his fingers. But there is no known write mechanism by which the brain could permanently store data.

When it comes to read functionality, we know of no mechanism at all for such a thing. There seems to be absolutely nothing in the brain similar to the read-write head of a hard disk, something that might allow the brain to “zoom in” and read from one particular location. A system has to be organized in a very specific way for read-write functionality to be possible, and the brain seems to be organized in no such way.

Conclusion

Our neuroscientists tend to dogmatically speak as if our memories are all stored in brains, but this is more of an ossified dogma rather than a truth determined by observations. Neuroscience itself undermines such a doctrine, by indicating that there is no stable component that the brain could be using to store memories lasting decades. Comparing the brain to a computer, we find that the brain has nothing like any of the 7 main things that the computer uses to store and retrieve data. But our minds recall obscure information instantly, and a single phrase may get you to instantly recall some old tune you have not heard in 50 years (as recently happened to me).

The discussion above should be very discouraging to anyone who hopes to explain how brains could achieve the memory capabilities of human minds. To such a person I must merely say: you're barking up the wrong tree. The feats of our minds cannot be explained solely in terms of the brain. We must postulate some psychic or spiritual component to account for the feats of our minds, something beyond the brain. Such a thing is needed to account for the wonders of psychic phenomena, and is also needed to account for the ordinary marvels of the human mind such as the instantaneous recall of childhood memories. 

Postscript: We may imagine the following conversation between a curious young boy and a distracted mother walking on the street. 

Boy: Mommy, who made the clothes I wear? And who made the TV shows I watch? And who made the cars I see? And who made the street lights?  

Mother:  The answers are simple, my son. They are: Santa Claus, Santa Claus, Santa Claus, and Santa Claus.

We can also imagine a similar conversation between a philosopher and a neuroscientist.

Philosopher: From whence comes that hint of the transcendent we feel when we look at a sky ablaze with stars?  From where do our loftiest ethical principles arise? Why do we lie awake and ponder the weightiest riddles of existence? How do we ever grasp the most abstract notions such as the idea of the universe and the eternal laws of nature?

Neuroscientist:  The answers are simple. They are: neurons, neurons, neurons, and neurons.

Such simplistic answers are convenient, but should we not suspect such complex questions have equally complex answers? 

It's Looking Like We Don't Live in a Carl Sagan Universe

The Search for Extraterrestrial Intelligence (SETI) is in the news. The biggest recent effort to search for extraterrestrial civilizations is a project called Breakthrough Listen. The project is a ten-year project that began in 2015 with 100 million dollars in funding from a Russian billionaire. A few days ago, the project announced what it had found so far.

A few web sites made it sound as if something very interesting had been found. The Daily Star site had a headline: “Alien shock as scientists reveal 11 mysterious ‘signals’ hailing Earth are probed for UFOs.” The web site sputniknews.com had a headline, “SETI's Largest Project Reveals That 11 Signals From Space May Point to Aliens."

But when you actually read the release, you will hear about nothing indicating success. The 11 signals are simply the “highest ranked” in terms of strangeness. The press release concedes that “the search has not yet detected a convincing signal from extraterrestrial intelligence.” The press release gives us no details of any one of these “highest ranked” signals, which suggests that none of them is particularly interesting. They are probably just emissions from natural phenomena or from earthly sources.

This recent paper reports on a search of 5600 nearby stars looking for signs of laser signals that might show up in the spectra of the stars. The scientists reported this:

We found no such laser emission coming from the planetary region around any of the 5600 stars. As they contain roughly 2000 lukewarm, Earth-size planets, we rule out models of the Milky Way in which over 0.1% of warm, Earth-size planets harbor technological civilizations that, intentionally or not, are beaming optical lasers toward us.

A previous scientific paper reported on a search for optical signals coming from sun-like stars. 10,000 such stars were searched over the course of two years, but no such signal was found. Extensive searches looking for radio signals from extraterrestrials have also come up negative. This paper describes a negative search for alien radio signals coming from 9293 stars, consisting of 19,000 hours of observations carried out between May 2009 and December 2015.

Another search for extraterrestrials looked for signs of large-scale engineering in distant galaxies. Since the universe is about 13 billion years old, if an extraterrestrial civilizations had appeared on a distant planet, it would be more likely to have appeared billions or millions of years ago. Such a civilization might have evolved into some state of godlike power, allowing it to re-engineer entire solar systems or entire galaxies. But a search of 100,000 nearby galaxies looking for signs of extraterrestrial engineering came up empty.

These findings all cast doubt on the vision of the universe advanced by the late astronomer Carl Sagan. In books and a television show (the original version of the Cosmos series), Sagan advanced rather dogmatically a set of ideas that were widely influential. His ideas are summarized in the visual below:

When I was a young man in my early twenties, Carl Sagan was at the height of his influence, and I bought quite a few of these ideas. But now quite a few of these ideas seem dubious or untenable. As a whole, the Sagan Creed lacks coherence, and parts of it seem to contradict other parts of it. For example, if it were true that the galaxy was teeming with so many extraterrestrial civilizations, why should we not expect that some of them are visiting us now, or have visited us in the past? Oddly, Sagan himself wrote a book briefly hinting that some archaeological evidence suggested extraterrestrial visits in the past, but then began denouncing that idea when it was vigorously advanced by Erich von Daniken. Was he jealous that von Daniken's books advancing the idea made many times more money than Sagan's own book briefly suggesting the same idea?

Another inconsistent part of the Sagan Creed is its insistence that extraterrestrial intelligence is very common, but that mere blind chance is all that is at work to produce extraterrestrial life and extraterrestrial intelligence. Given all the great difficulties in life appearing by chance (discussed here), and the equally great difficulties of intelligence appearing by chance, we should not expect that extraterrestrial intelligence should be common if nothing special is at work in the galaxy, and that just blind chance is at work. But one has a consistent position if you maintain either (1) that some great force of cosmic teleology is at work, and that intelligent life has commonly appeared, or (2) that nothing but blind chance is involved, and that intelligent life is incredibly rare, requiring extremely improbable accidents.

Another inconsistent part of the Sagan Creed was its assumption that extraterrestrial civilizations would be using radio for communication, matched with the claim that such civilizations are probably millions of years older than ours. If such civilizations were so advanced, should we not assume that eons ago they switched to something far more advanced than radio communications?

Another inconsistent part of the Sagan Creed was his repeated insistence on both the claim that extraterrestrial life is very common, and that extraterrestrials would never look anything like humans. He justified the idea that extraterrestrials would never look like humans on the grounds that there are trillions of possible paths evolution might make. But the same reasoning can be used to argue that extraterrestrial intelligence should be very rare, on the grounds that there are a billion ways for life to become successful without becoming intelligent (all far easier to do than for life to become intelligent).

In this essay, Sagan said, “When we do the arithmetic, the number that my colleagues and I come up with is around a million technical civilizations in our Galaxy alone.” The statement is nonsensical. First, it implies a consensus on the topic, when no such consensus ever existed, with estimates of the number of extraterrestrial civilizations in our galaxy ranging from 0 to a billion. Second, there was never a sound basis for drawing such a conclusion. Suppose we calculate the odds based on the difficulties of a chance appearance of the most simple type of life (requiring cells, DNA, a genetic code, and many types of proteins, which are each exceedingly unlikely to appear by chance), without assuming some special cosmic teleology that might improve the odds. Then the answer you get is that we should expect no other life form to have arisen anywhere else in the galaxy. That's not even considering the difficulties of intelligence appearing after life has appeared.

A very strong argument can actually be made that when estimating the number of extraterrestrial civilizations in our galaxy, it makes no sense to make intermediate estimates such as Sagan's (by intermediate estimates I mean those which estimate a number of civilizations in our galaxy greater than 100 but less than a billion). The argument has to do with interstellar colonization. Suppose there were, say, 100,000 extraterrestrial civilizations that independently arose on other planets in our galaxy. Even assuming very slow interstellar travel, there would have been abundant time (more than a billion years) for interstellar colonization, in which many times a civilization spreads out to colonize nearby solar systems. So within 100 million years or a billion years, an original population of 100,000 civilizations on 100,000 planets should inevitably expand out to inhabit billions of planets. The same thing should happen even if there were only 1000 extraterrestrial civilizations. So based on interstellar colonization considerations, it seems that it makes no sense to estimate that there exist something like a million civilizations in the galaxy. But such a consideration does not rule out a much higher estimate, that there might be billions of planets inhabited in our galaxy.

The previously discussed results of the Search for Extraterrestrial Intelligence (SETI) suggest that Sagan's estimates about the number of extraterrestrial civilizations in our galaxy were way off the mark. They suggest that our galaxy does not seem to be teeming with a million or so extraterrestrial civilizations as Sagan imagined. The very strong evidence for psychic phenomena (such as I discussed here, here, here, and here) suggest that Sagan was also dead wrong about paranormal phenomena, which he attacked in his book The Demon Haunted World.

Carl Sagan was a pleasant, sincere fellow who did lots of good work, but it seems that we don't live in a Carl Sagan universe.

One of the more dubious things Sagan did was to get NASA to put information disks in the two Voyager spacecraft. Sagan chaired a committee that took almost a year to select the contents of the disks. The idea was that the disks would be a record of human activities that might be picked up in the distant future by some extraterrestrial civilization when the Voyager spacecraft left the solar system after exploring Jupiter and Saturn. If our sun were the size of a grapefruit, the nearest star would be 2500 miles away. Given the incredible vastness of interstellar space, the chance that either Voyager spacecraft will be picked up by an extraterrestrial civilization is basically zero. So spending lots of time preparing such a disk for the Voyager spacecraft was a silly idea (conversely, putting such a disk on one of the Apollo lunar landing vehicles would have made sense, for there would have been a reasonable chance of discovery by extraterrestrial visitors in the distant future). But NASA went along with the Voyager disks idea, because Carl Sagan was pitching it. When you're a celebrity scientist, it's almost like you are some Svengali or Pied Piper who can get people to believe in something you sell, even if it makes no sense.