What exactly have you tried? Does the dog make messes all over, or just in one or two spots? Is the dog on a feeding schedule or do you leave food out? Does the dog have a crate? I think everyone here could be more helpful if we knew some specifics. Thanks!

I think it helps to remember that some dogs, just like people, you just can't reason with. Also it take's a very big commitment from you. We all love our dogs, and playing the bad guy can be really hard, but it's for the best interest of you and your pet. Dog's are pack animals, so if they are not following your commands it's most likely because they see themselves as your superior. Maybe try being more stern with the dog. Praise him when he goes outside, but raise your voice and show your dominance and dissapointment when he goes inside. Point out the "mistake" take the animal outside and tell them that they need to do it out there. Keep your language short and consistant, i.e. no, yes, go pee outside, bad boy to go pee inside. Don't switch to it to "make a tinkle" the next time because the dog wont be able to link them together. Good luck