An elderly professor, well-known for his penetrating insights into the natural world, steps up to the lecture podium to deliver the findings that will mark the culmination of a distinguished career. He clears his throat, and announces:

All swans are white 

The audience rises to its feet in rapturous applause. That is, all except a young Australian scientist at the back. She calmly walks to the stage and gives the professor a picture from her own personal collection:


A picture of a black swan.


Who is the more scientific here? The professor who has spent a lifetime amassing mountains of evidence to support his views, or the young up-start who proved him wrong in an instant?


According to the Austrian-British philosopher Karl Popper, the Australian scientist is the most scientific. But the issue the question touches upon is one that has affected science since the eighteenth century. Popper claimed to have solved it.

You see, according to the scientific method we should make observations, and when we’ve collected enough, we can make generalisations about the world, creating scientific theories.


The question is: how can we be sure we have enough observations?

Its one thing to say that all the swans you’ve observed have been white, but quite another to claim that this means every swan is white. Its making a jump from the observed to the unobserved, from a select few to the potentially infinite.

This problem is known as the ‘problem of induction.’


Its also the wrong way to understand how science works, says Popper. Instead of trying to prove our scientific theories are true, we should spend our time trying to prove that they are wrong.

To falsify them, rather than confirm them.

In fact, Popper goes so far to say that a theory is not scientific unless it can be falsified. Pseudo-scientific theories are far too vague to be tested, he believes. Sometimes pseudoscientists spend far too much energy devising ad-hoc hypotheses to show how facts which would prove them wrong actually prove their theory right.

A theory is scientific for Popper if it could be proven wrong, but has not been, the more attempts to disprove it the better. Instead of making bland, yet safe, hypotheses that will survive our tests, Popper believes that scientists should make as outlandish theories as possible.

Most will fall, but the ones which don’t will mark a great leap in our knowledge of the universe, and when it eventually fails, it will have bypassed the notorious problem of induction.

Popper’s is a seductive view of science and of the work that scientists do. Not humble calculators but scientific adventurers, boldly ridding us of our preconceptions and false ideas.

But was Popper being too hasty? Are there scientific theories we should hold on to despite one or two pesky little refutations? Is this how scientists behave in their day-to-day life? And just what are these ‘tests’ that he likes so much?