Euthanisa for Max? (A labrador collie)

NVDL: My father has 4 dogs and cat, and one of them, Max has developed paralysis in his hind legs. Is Euthanasia the answer?

It's ironic because Max, the only male of three labrador puppy pups we kept, was by far the most fleetfooted, the most athletic of the siblings. Now he's a cripple, and the other two show now symptoms.

I saw Max when we got together to watch the SA vs USA game. Whenever the Boks score we naturally stand up and shout and then the Jake Russell (Jody) goes ballistic, which causes the rest of the mutts to bark like mad. I noticed Max's bark had a painful tjank to it. It wasn't the baritone bark we're used to hearing.

It's gotten so bad that the poor animal has been dragging his legs around behind him, cutting open his feet and heels on the tiles in the lounge. My brother at one stage 'bandaged' these bleeding wounds with socks. The consensus emerged that my father was a cruel and heartless man for allowing this animal to endure terrible agony.
When my dad arrived back from Botswana I asked him about it. He said he'd taken Max to a public hospital (hidden under a sheet, sitting on a wheelchair) and scanned the animal in those chambers...Radiology departments that check for cancers, brain tumours, neurological disorders.*

Of course it is illegal to scan animals in a public hospital, but the nearest animal hospital that provided this was in Pretoria. So they didn't find tumors on Max's spine. It's some kind of spinal disease associated with rheumatism. I'm a bit fuzzy on the details. The point is it wasn't curable, so Max's condition will get worse.

So the question came up, is it better to put the animal down? It's an easy answer on the face of it. Looking a bit closer, as I think my dad is, he sees the whole life of the dog, and that his two siblings are perfectly healthy. And he points out that when he goes to the shops in his bakkie, the dog does his best to get to and through the door. This, he says, is evidence of the animal's will to live.

Because Max can't talk, we have to make a judgement. Is the pain of life greater or less than the pleasure/will to live? There's another philosophical question to ponder too. Whatever your religion, most people would probably agree that when pets or any other animals die, that's it for them. The start of an endless sleep. So if you're this animal, it's an absolute ending.

So I see my dad's point of view. It's based on be-the-creature. If you were Max, even if you were in pain, would you want to speed up your demise, knowing that everything is once-in-a-lifetime? It's also a psychology people ought to consider, even if they don't accept. If it is true that we have one life (and in a sense, this life on Earth IS our only life), then EVERY day is a precious gift, and each and every murder and crime is a a great and terrible tragedy. That this isn't the reigning psychology, that this isn't the contemporary wisdom of our time is a collective insanity that we need to wake from each and every day.

Please provide your suggestions in the comment field below because it's something we're debating as a family, and not sure what to do.
*This procedure alone cost around R6000.