20 Famous Thinkers Who Were Wrong About Almost Everything

This Roman physician convinced the world for centuries that health depended entirely on the balance between blood, phlegm, black bile, and yellow bile. If you weren’t feeling well, he would simply suggest a good bloodletting to restore that balance. We now know that germs and genetics play a much more important role than your “humors.”

Ptolemy was a mathematical genius, but he placed the Earth at the center of the universe, with everything else revolving around us. His complex system of “epicycles” was designed to explain why the planets moved in strange ways, making the cosmos look like a complicated clock. Eventually, we came to understand that it is actually we who revolve around the Sun.

A giant in the field of thermodynamics, Kelvin calculated the age of our planet by measuring the time it takes for a molten ball to cool. He concluded that the Earth was only 20 to 100 million years old, which is a considerable underestimation. He knew nothing about radioactivity, which provides the internal heat that keeps our world much older than he imagined.

Lamarck believed that if an animal worked hard to change its body during its lifetime, those physical changes would be directly passed on to its offspring. In particular, he suggested that giraffes had long necks because their ancestors constantly stretched to reach leaves high up in the trees. Genetics has ultimately proven that it is not possible to pass on the “gains” achieved at the gym to one’s offspring.

This famous alchemist believed he could grow a fully formed human being in a jar using rather repulsive ingredients, such as biological waste. He was convinced that life could arise spontaneously through these strange chemical concoctions. Fortunately, modern biology has replaced his “babies in jars” with the reality of cell reproduction and DNA.

Bacon is considered the father of the scientific method, but his experiments could sometimes be somewhat ill-advised, or even fatal. He died after attempting to prove that stuffing a chicken with snow would preserve its meat, catching a bad cold in the process. While he was correct about refrigeration in general, his specific theory on how cold interacts with meat was rather primitive.

Before formulating the laws of planetary motion, Kepler was obsessed with the idea that the universe was made up of perfect 3D shapes. He tried to fit the planets’ orbits into a nested series of Platonic solids such as cubes and pyramids. It was a beautiful idea, but the universe turned out to be much more disordered and elliptical than his elegant shapes suggested.

Descartes was a brilliant mathematician, but he held the curious belief that animals were nothing more than mechanical automatons devoid of a mind. He claimed that they could neither feel pain nor think, since they lacked a rational soul—a belief that led to some rather cruel treatments in the name of science. Today, we recognize that our furry friends have complex emotions and a very real nervous system.

Leibniz argued that, since God is perfect, we must be living in the best of all possible worlds. He believed that every tragedy or imperfection was, in fact, necessary for a greater harmony that we simply could not perceive. Today, most people find it difficult to accept this idea, especially when we consider the extent of the chaos that has marked history.

Hobbes was a heavyweight in politics, but he shouldn’t have tried his hand at geometry, as he claimed to have solved the impossible problem of “squaring the circle.” He spent years debating with actual mathematicians, insisting that his flawed proofs were revolutionary. History remembers him for his social contract, but his mathematics remains a cautionary tale of overconfidence.

The man who gave us the system for classifying species also included a section for “monstrous” humans and mythical creatures such as hydras. He sincerely believed that these beings existed in remote parts of the world and assigned them official scientific classifications. We eventually realized that these stories were merely sea legends and not biological reality.

For a long time, Redi fought against the popular belief that maggots appeared as if by magic on decaying meat. Even after he proved that flies laid eggs, many people continued to believe that tiny “germs” could spring up out of nowhere. It took time for the world to accept the idea that life can only come from another form of life.

Harvey correctly understood how blood circulates, but he was completely mistaken about why the heart beats. He thought the heart acted like a furnace to warm the blood, rather than simply as a muscular pump. He viewed the body as a kind of steam engine, unaware of the purely mechanical nature of our cardiovascular system.

Freud is an iconic figure in psychology, but his early “theory of seduction” attributed nearly all mental disorders to specific traumas experienced during childhood—traumas that often never actually occurred. He later abandoned this idea, but his obsession with unconscious drives still prevented him from understanding how brain chemistry works. Most of his theories are now considered more a matter of literature than of medical science.

You know his theorem, but you probably don’t know that Pythagoras had a deadly spiritual phobia of beans. He believed they contained the souls of the dead and forbade his disciples from touching them. Legend has it that he would rather let himself be captured by his enemies than cross a field of beans to escape.

The “father of chemistry” spent much of his life trying to turn lead into gold using secret potions. He believed that there was a universal solvent capable of breaking down any metal and transforming it into a precious metal. Although he helped lay the foundations of chemistry, his heart remained tied to the magical world of alchemy.

This Greek philosopher proposed that everything in the world was held together or kept apart by two literal forces called “Love” and “Conflict.” He did not view them as metaphors, but as actual physical elements that governed the movement of atoms. Science eventually replaced these romantic notions with boring concepts such as electromagnetism and nuclear forces.

Franklin did remarkable work in the field of lightning, but he believed that electricity was a “fluid” that flowed from one object to another like water. He believed that an excess of this fluid caused a positive charge and that a deficiency caused a negative charge. Although his calculations were correct, electricity is actually the movement of electrons, not some mysterious liquid.

Lucretius was an ancient poet who had correctly surmised the existence of atoms, but he also believed that they possessed “free will” and could deviate as they pleased. He used this “deviation” to explain why humans have a choice, which is not exactly how physics works. He was a visionary, but his understanding of atomic mechanics was more poetic than practical.