Originally Posted by jisincla
That is true, and I have done enough research to be satisfied that the animal nutrition experts who developed their diet are qualified to do so, and the veterinarians who monitor their health would tell me if they had any diet-related problems. I have always made a point of informing my cats' veterinarians about the diet I'm feeding, and asking the vets to check carefully for any sign of nutritional deficiencies.
Empirical evidence means that you have taken a random sample of cats who have a similar characteristics - healthwise, gene-wise, etc. You cannot simply conclude that you have dispelled a theory which has been tested by qualified scientists over many years because you have fed a few cats of your own a vegan diet. Sure, your cats may have lived 14 years but this could be due to luck, genes or whatever. Genetics, in my opinion, play a huge role in a being's health. Just think of people who can eat anything, junky, fatty, whatever and they never get sick or gain weight. So unless you can control for genes and other factors, you cannot claim your cats have provided empirical evidence. Evidence perhaps of the circumstantial kind or personal kind but not empirical.
While it's good to inform your vet about what food you're feeding, how much do they really know about nutrition? Granted, the up and coming vets are more informed but in general, vets learn about nutrition from Hills or whatever other company that sponsors their courses. Ultimately, they know it's their clients' decision about what to feed their pets and if they know your personal beliefs, are they really going to challenge you? Would you change the diet if your vet said to feed all meat? Possibly yes but it is also plausible that your vets may not want to offend you.
You just have to look at wild cats and see what they eat. They eat meat. They have not evolved much so even historically, they ate meat. Nothing empirical about that.