Well I am not sure you will be able to change his mind if he is so set on not having a dog, what are his main reasons for not wanting one?
My partner hated cats, when he moved in with me, he just had to get use to the cat being around, now he loves her to bits.
If your partner has been spoint in the past, maybe he is just being really really stubborn.
I was in a similar situation, and my ex partner arrived home to their being a cat in the flat! He didnt get a choice, he soon came to love the cat, but this might not be the best solution as I am not sure what your partner would do.