There is an intellectual sin that is very common among many modern scientists: the sin of speaking as if they had explanations that account for long-standing puzzles of nature, even if they don't really have such explanations, but at best merely have small fragments of such explanations. Imagine a person who doesn't have a blanket, but merely has some threads picked up from various places on the floor. Such a person might try to call those threads a blanket, or most of a blanket, but that would be quite an exaggeration. Similar to such a person, many a modern scientist speaks as if he is some great knowledge lord who has mastered some deep puzzle of nature, when he is merely someone familiar with a few things that might be fragments of the solution of such a puzzle (like individual pieces of a 50-meter-long jigsaw puzzle).
I read an example of this type of exaggeration today in a post by cosmologist Ethan Siegel. Siegel makes this claim: “The inflationary Big Bang Universe, with radiation, normal matter, dark matter and dark energy, explains the full suite of absolutely everything we’ve ever observed, and nothing else does.” Is this statement true? No, it's a ridiculous case of overselling a very patchy theoretical framework.
First, the inflationary Big Bang universe theory does not explain the origin of the universe itself, leaving it as a complete mystery. Second, there are many important physical things unexplained by the inflationary Big Bang theory -- things such as the hierarchical structure of the universe, the CMB cold spot, the persistence of spiral galaxies, and the fine tuning of fundamental constants that makes possible a habitable universe. Third, we have no real understanding of either dark energy or dark matter. Neither is part of the Standard Model of Physics. The very terms “dark matter” and “dark energy” are pretty much just euphemisms for “some kind of mysterious something that we know nothing about.” So claiming that explains something (or is part of an explanation) is erroneous.
When physicists and cosmologists actually do calculations relevant to the issue of dark energy, they get a shocking result: that the vacuum of space should be filled with a dark energy or cosmological constant more than a billion trillion quadrillion times (more than 1,000,000,000,000,000,000,000,000,000,000,000,000 times) larger than we observe. This is the completely unsolved “cosmological constant” problem (sometimes called the vacuum catastrophe) that has long haunted physics and cosmology (it is discussed here). Claiming that dark energy is part of some explanation of “absolutely everything we've ever observed” is hilarious. Better to say that dark energy is part of the reason we can't even explain the simplest thing we can think of (the vacuum) – because according to physicist's calculations the vacuum should be so packed with dark energy that it should have more mass-energy than solid steel.
There are other fields of inquiry in which scientists claim to understand puzzles of nature they do not understand, by trying to exaggerate what they have learned. One such field is the field of biology. Here the most prominent cases of explanatory exaggeration involve evolution and natural selection. We commonly hear scientists speak as if evolution is some magic potion that explains “in one fell swoop” how it is that there came to be beings such as us on this planet.
But it isn't. While evolution and natural selection are very probably important pieces in the puzzle of the origin of intelligent life on our planet, they are probably no more than pieces in that jigsaw puzzle. For one thing, neither evolution nor natural selection can explain either the origin of life or the origin of the genetic code. That's because both evolution and natural selection require life itself, and you can't explain the origin of life by something that requires life.
Moreover, humans have many special mental and spiritual capabilities that are extremely difficult or impossible to explain by natural selection or evolution. Humans have inner selves and personalities. Humans are great at language, and at formulating very abstract ideas. Humans are capable of wonder, joy, love, guilt, compassion, imagination, and spirituality. Humans can create art and literature, ponder their own deaths, wonder about the meaning of life and the nature of the universe, create and follow moral codes, and consider philosophical matters. As argued here, it is hard to explain most of these things by evoking evolution or natural selection, because most of them have no survival value, from an evolutionary standpoint of making an organism more likely to survive until it reproduces.
Things evolution has a hard time explaining
How did humanity get these things? We don't know. The modern biologist offers an unconvincing, simplistic explanation – “it all just came from evolution.” But the actual explanation is probably far deeper and more complex. I can understand why the biologist would wish to offer this answer of “it all just came from evolution.” It is always better to be able to say, “I have the answer to this great mystery of nature,” than to say, “I have but a few tiny fragments that may one day be of use in solving this great puzzle.” It is always more pleasing to put yourself on a pedestal marked “Great Lord of Knowledge” than to humbly realize that the puzzles of nature vastly exceed your meager understanding.
If you point out the explanatory limits of evolution to a biologist, you may be attacked as an evolution denier, even if you did not at all deny it, but merely pointed out its explanatory limits.
Another example of inflated knowledge pretensions involve claims about the human brain. Scientists have done some brain imaging studies showing how parts of the brain light up differently under different conditions. If you read some enthusiastic reports of such studies, you might get the idea that scientists have a deep understanding of how our brains work. But they don't.
As the book Mind and Brain: A Critical Appraisal of Cognitive Neuroscience makes clear, brain imaging studies have cast relatively little light on the mysterious workings of the brain. Here are some points made on page 365-366 of the book:
Brain imaging meta-studies show that when the results of a number of experiments are pooled, the typical result is to show activations over most of the brain, rather than convergence on a single location... Considerable portions of modern cognitive neuroscience's empirical research support the idea that every cognitive process is a product of the action of a highly integrated system in which many parts of the brain interact rather than function independently as isolated regions...There has been little replication of most findings...No part of the brain has only a single, unique function...Clinical data, especially with traumatic injuries, do not display high degrees of correlation between particular brain lesions and cognitive states.
It would seem that those who claim to understand the brain through some kind of “this part does this thing” approach are exaggerating their understanding, and that the brain is still a deep, intractable mystery. Indeed, there is every reason to suspect that we are centuries away from being able to understand the brain's secrets.
How is it that these examples of knowledge hubris become so widely accepted? How is it that again and again our scientists get people to think that they are knocking on a door marked “Final Explanation” when they have often just walked a few paces down the long, long road that leads to that door? Part of the reason is that it's like a school where there are no teachers to give scientists grades, and they can make their own grades. Imagine if you were at a school without any teachers, one in which you give yourself a grade. You might learn just a few facts about modern history (such as the fact that soldiers landed on a beach on June 6, 1944, and the fact that some bombs were dropped on December 7, 1941). You might then conclude that because you had learned these things, you now had a deep understanding of modern history, and give yourself an “A” in the Modern History course. There would be no one around to say, “no, no, you have learned just the tiniest fraction of what you need to know to understand that topic.” Similarly, there is no one around to correct the scientist who fancies himself a knowledge lord after learning but a few paltry fragments of nature's vast and deep secrets.