Van Zant's Six Cardinal Questions

In 2012 I spent some time in Rob Coppes' lab at the University Medical Center Groningen, where a plain poster on the wall caught my eye: six numbered questions under the title "Van Zant's Six Cardinal Questions of Scientific Investigation." I took a photo, and I've been thinking about those questions on and off ever since, which is more than I can say for most things I photographed that year.