One of the most striking features of the disease is the disproportion between its severity and the simplicity of the cure. Today we know that scurvy is due solely to a deficiency in vitamin C, a compound essential to metabolism that the human body must obtain from food. Scurvy is rapidly and completely cured by restoring vitamin C into the diet.

Except for the nature of vitamin C, eighteenth century physicians knew this too. But in the second half of the nineteenth century, the cure for scurvy was lost. The story of how this happened is a striking demonstration of the problem of induction, and how progress in one field of study can lead to unintended steps backward in another. //

Finally, that one of the simplest of diseases managed to utterly confound us for so long, at the cost of millions of lives, even after we had stumbled across an unequivocal cure. It makes you wonder how many incurable ailments of the modern world—depression, autism, hypertension, obesity—will turn out to have equally simple solutions, once we are able to see them in the correct light. What will we be slapping our foreheads about sixty years from now, wondering how we missed something so obvious? //

But the villain here is just good old human ignorance, that master of disguise. We tend to think that knowledge, once acquired, is something permanent. Instead, even holding on to it requires constant, careful effort.