Most people have heard of Louis Pasteur, a famous French biologist and chemist who lived during the 19 th century and invented “pasteurization.” As a proponent of the “germ theory of disease” (the belief that disease is caused by germs), Pasteur is one of the fathers of modern medicine.  However there were equally well-known scientists in Pasteur’s day who didn’t agree with him. Germs, they argued, couldn’t gain a foothold in a truly healthy body.  Chief among these critics was physiologist Claude Bernard. Bernard held that our body’s “inner terrain” (or immune system) determines our health. He is unknown today because his ideas lost out to the germ theory. But Pasteur himself is reputed to have said on his deathbed, “Bernard was right. The microbe [germ] is nothing; the terrain is everything.”  So it’s dismaying that the advice given to the public regarding COVID-19 seems to be based on the theory that “the virus is everything; the terrain…