Whenever I hear "purely positive" training, I always cringe because I know there's going to be some negative punishment. The fact you don't give the dog a reward if he thinks his action will earn him one is negative punishment. That's just the way it is. To be truly "purely positive" you have to give a reward for EVERYTHING the dog does. That reward doesn't have to be food or even a click - it could be just giving him what he'll want in that situation.
So, tomorrow, I will try just that, just to see what happens. Well, I guess even then it's 99% because he still will not be allowed to do anything that disrespects someone else (or their property/pets/family), or anything that is unsafe, either for himself or others, but I don't think that will happen. It hasn't in a long time.
Otherwise, everything he does will get something he'll like/want. It will be interesting to see how this works out and what might change going forward, especially since there's not a lot of punishment going on here anyway, mostly during "formal" training (shaping, marker and reward or nothing), but there's not necessarily a lot of overt reward either. Most of the things he does, he's just "allowed" to do and generally gets little reaction from me.
It will also be interesting to see what he does differently, if anything. Perhaps he won't be able to tell a difference, and just act as he always does. Maybe I'll end up getting too many offered behaviors, where it will become more of an inconvenience than anything else, while doing nothing for him. Or perhaps it will have a...ahem...positive impact any maybe he gains more confidence or somehow all of his tricks and such become better.
Can't wait for tomorrow actually!