If dogs wore pants, they would wear them on their hind legs only (not on all four).

The point of pants is to cover the legs, to protect them from getting dirty from mud or dirt. Covering the back legs, while leaving the front legs exposed makes no sense as the front legs are easily as capable of getting dirt on them as the back.

Sweaters and shirts are a bad example as they are only there for decoration on a dog. A better example would be, if a dog were to wear shoes, would it only wear a pair of shoes on the hind feet, or have two pairs covering both sets of feet?

I believe this is the way dogs would wear pants for two reasons.

Well... I'm not sure this satisfies Rule 1... but since this is a slightly silly view, I will challenge this part of it.

They would wear pants like that, not because of the reasons you specify, but because it would actually work, just like why we wear pants like that.

The first picture presents no notion of how those pants would actually stay up, and in fact it's absurd to think that it would be possible.

A jumpsuit that went all the way over the dog's back, sure... but not "pants".

We wear pants that way because it's possible to have pants stay up if fastened about one's waist.

Four legged pants would be held up way better with suspenders over the torso.

https://thehydrant.files.wordpress.com/2011/11/z1.jpg

See what a dog who runs through snow looks like. Look at the sadness in their eyes, their legs caked with snow, their belly covered in more.

Would you really deny a dog the warmth and comfort of full leg jeans that protected them? Would you look into that dogs eyes and tell it that their legs were going to freeze off so they can look stylish?

http://www.digmydog.org/images/dogs/1111/-dogs-1320589111.jpg

Or this dog.

http://media.boreme.com/post_media/2008/dog-snow-legs.jpg

Or this one. Their pain deserves an answer.

Humans use pants to protect the lower part of the body. That's why pants tend to use different, stronger materials than shirts. In the case of a human it only needs to cover 2 legs. But since dogs walk on 4 legs, they would need 2 pairs of pants. If dogs were to walk in it's hind legs (like humans) your point of view would make more sense. I'm talking in a practical way, probably for styling dogs it would be better the like you say.

PD: With my impressive skills in paint i made this.

What about snow pants or waders? In those cases, the pants are really meant to allow you to stand in something (snow or water) without getting cold or wet. Only the first picture would allow those pants to fulfill their functions.

Edit: this is true for regular pants too, to a lesser extent. If you're going to be walking through prickers or in a tick-infested area, you want long pants over shorts, even in the heat of summer, for the protection it provides. You only get that protection if all legs are covered.

This hypothetical is fascinating to me for some reason. So why are dogs wearing pants, is it like pets that people are dressing up? If I actually wanted my dog to wear a pants and top outfit, what I would do is have the pants be a onesie with a butt flap and then a sweater/shirt over the top. If a dog wore pants like in image two you'd have to take them off entirely for the dog to go to the bathroom.

if you look up dog jackets, you'll see most of them go over their backs and have a strap under their front legs but their bellies aren't covered. if they wanted the bottom half of them covered they'd wear pants that go on all for legs and match up to the line of the jacket. if you're just going for style, they'd wear the two leg pants, but it just wouldn't make sense to leave their front legs out if they have pants and a jacket fire protection from cold or mud.

Would the four legs pants even work mechanically without restricting the movement of the dog. Dogs do a lot of stretching along that direction while running. I don't think that four legged pants would be able to be made tight enough to stay up without being so tight that they would be uncomfortable or make it very difficult for the dog to run.

The Seven Commandments from Animal Farm state the following.

No animal shall wear clothes.

assless chaps are pants. chaps wouldnt make any sense on a dogs front legs. Hence dogs would wear chaps on their rear legs. There's no way they'd wear different kinds of pants on different legs, because that's plain stupid. QED

If dogs wore pants they'd have to wear them on their front legs because they have no hands and would wind up pissing and shitting themselves otherwise.

Instead of working in our reality where people dress up dogs (Which would result in the second picture because it's easier.) let's instead look at the needs of a dog for pants. Yes, this will presume fully anthropomorphised dogs in their current biological form.

In general they don't need clothing for warmth. Unless they were to absentmindedly shear off more than intended. Then like a ballcap worn constantly to hide a bald spot, the pants would help cover this up.

The pants wouldn't be worn for decency, since in order to accommodate the tail... the butt is exposed anyway. Plus for the guys at least, the lack of the ability to zip and button on short notice (No thumbs) would suggest a cleverly sewn "pocket" that would open when the leg was lifted for needs.

So the reasons to wear them would be utility and fashion.

For fashion, yeah... hind legs only makes sense. Like going to a beach in your bathing suit.. show off that gut boy. whoooosssaagoodboy? esss ooo aaahhhh... essss ooo aaaahhhh.

But for utility? The pockets on the hind legs are almost completely useless for anything you need to get to quickly. However a more overall/jumpsuit like garment would allow the dog to access their belongings more readily. Since they don't have thumbs, the only way they have to grasp most objects is with their mouth. So something like this but for a dog. Pockets would be on the side similar to the packs worn by service dogs now. The part of their chest they couldn't reach would be a convenient spot to put a pocket for their bus pass too.

The first image has a clever idea, but they would need to be held up by suspenders and go over the hips in order to stay in place, so it's a clever thought with poor design. (Yeah, you could get around that.. but why bother when there are better alternatives?)

One point made in one of the other threads about this is: Dogs may not have the same motivations for wearing pants that we do. Why does the fact that it corresponds to how we wear pants matter at all?

One practical thing mentioned in this thread is running through the snow and such -- in that case, it's important to protect the dog's legs and belly, as those are the things actually exposed to whatever the dog is running through.

One thing mentioned in the other thread is that leaving the dog's ass hanging out is a feature, not a bug -- this is how dogs meet each other, by sniffing each other. It would be the equivalent of covering up a person's face. So your proposed way for a dog to wear pants is actually a doggie-burka.

Dog jackets (as opposed to sweaters) usually go over the back, matching the dog in the first picture.

Neither picture is accurate for this scenario. Pants, assuming they're wearing them for protective purposed, would almost certainly be a two piece affair for dogs. You may as well just think "pants and sweater" but both made of the same material. The first picture is completely retarded as the pants are not secured and will fall as soon as the dog starts walking, if not sooner. It takes no advantage of the body shape to hang there without assistance. The second picture does an inadequate job. From the perspective of pants as protective equipment instead of fashion, it's like wearing one shoe.

So if dogs were to walk on two legs then they would be on the bottom half and their top legs would e like their arms and that's where they would wear their shirt so then if they had pants on all 4 legs how would they wear their shirts?!

I see other good answers but the fact of the matter is, pants are worn on legs. Dogs have four legs. You don't refer to the front legs as arms, you refer to them as legs because they continuously run/walk on them.

It's fashion and there are no rules. They have 4 legs which gives them more options. One day the want to go with pants on 2 legs, and the next they use the 4 legs pants.

tl;dr: they can wear it either way

Your bias is based on a single reference to how pants are worn, on a bipedal animal. Biologically, you would be correct, but from a utility standpoint, the purpose is to protect the legs not adorn the latter limbs. Don't send your poor puppy into the world unprotected on half the legs he has, get some real dog pants and ignore your anthropomorphic first reaction.

the first dog in the picture got som easy access to some ass sniffing, which is a must for any social dog.

What about a onesie? That covers their entire body and it prevents snow from getting in open areas!