My opinion is that dogs are shaped through both. I can't say it's 100% accurate on dogs, as there is no way to tell whether or not nature or nurture has certain impacts on dogs unless you take the time to find two dogs that were concieved by two sperm entering one egg, and having the egg split.

However, it is known now that both nature and nurture shape a PERSON to be who they are.

Tests have been done on identical twins for quite some time. Identical twins share the exact same genetic code, therefore are identical. So what do you do? Split them up! Scientists have taken identical twins who were seperated at birth and noted their personalities. They note any differences and similarities between the identical twins. It's actually remarkable what is always found. I remember one case where they reunited identical twins. One was a Jewish man who was raised by his father, and the other was a Nazi who was raised by his grandmother. So you'd think that because of their environment (nurture) they would act completely oppisite. Rather, they acted quite alot the same because of the genes they inherited (nature). Alot of times, when the twins meet, they go to the interview in the same make of car, wearing the same type of clothes (These personal preferences may not be inherited -- for instance, identical twins may both wear many rings because they both have pretty hands).

So, therefore we know that we aquire traits from both nature and nurture. That is why reputable breeding is so important! You want to make sure you have the best dogs that compliment eachother's personalities so that the puppies will inherit the wonderful personalities! And of course, you want the owner to provide a loving caring household so that the dog can further shape it's personality with nurture.

Sorry to ramble.