Vet tech for 5 years at an ER hospital and every time I had to go into a room to do a Euthanasia to go over paperwork and talk the pet parents thru the process I would say “We wish this was more of a science, but it really is closer to art. Sometimes things happen we can’t explain.” I can’t tell you how many times I saw patients that should have lived long healthy lives pass and less frequent but it did happen patients that are walking medical miracles that refuse to die. Or the 27 year old chihuahua that Satan refused to take, too hateful and evil. Every patient is different, we really just make our best guess based on lots and lots of evidence, but at the end of the day I would say the biggest thing I have learned, is just how much we don’t know. That’s not black and white at all, in fact Science is the continued pursuit of knowledge, and everything that’s unknown.