Can a M/s relationship really exist?

I'm having difficulty thinking it can.

An obedient sub looks like an obedient slave. They both are complying with their Dom or Master's wishes. The only difference that I can see if that one has the right to say 'no' and the other doesn't.

Or do they?

Let's look at a sub first. As I understand it, a sub can maintain hard limits - things that they absolutely will not do. Then they can have soft limits that they allow their Dom to push on and expand, perhaps turning them into normal activities, perhaps turning them into hard limits. They have the right to discuss and give feedback on the relationship as to what is working for them and what isn't. And at the end of the day, they have the right to walk away if they are not getting what they need or are being forced to do things they don't want to do.

Now a slave ... a slave by definition does not have hard limits. However, I wonder how many "no-limit" slaves would commit beastiality or sexual molestation of another human (especially an underage one) at the order of their Master. Wouldn't their own morals and ethics, not to mention the law, stop them from committing what comes down to crimes? So slaves still have hard limits; they just choose Masters who share the same ones so that they do not have to be subjected to the choice and therefore can still proclaim that they have no limits. Most people that I have talked to who live M/s 24/7 talk, discuss, and give feedback on the relationship. After all, it is between two people and a happy slave serves better than an unhappy one, right? Why wouldn't a Master want feedback? And, at the end of the day, a slave also has the right to walk away. No contract that you sign can bind you into slavery because the reality of slavery is against the law.

So what is a M/s relationship then? Is it just an elaborate pretense between two people? Is it that they make themselves believe that the slave has no right to the word "no"? Maybe it's my background in philosophy which has me questioning the logic, but I find it hard to believe that intelligent people could deceive themselves into thinking that they cannot say no. Maybe they choose not to say it but even in the choosing is an amount of power. You cannot give away the power that makes us all human - the power to make choices for ourselves.

My debate within myself as to how to identify seems to finally have stilled. I am a submissive because I do not choose to pretend. I wish to submit to a Dom and a sadist but I will never fool myself into thinking that I do not have a choice. And besides, the choice is what makes it hot.

It's like a conversation I was having recently about the differences between physical bondage and mental bondage. I said that physical bondage is very relaxing to me because I know that I cannot get loose until he lets me go. There is no fight in me and I can relax into the pain in a different way. Being told to get into a position or hold a position - much more difficult. I am participating. I am choosing to obey, to submit to whatever my Dom wants to do. I cannot pretend that it is not a choice because I am there, rather than not. I see the choice of submissive in the same way. I can choose obedience or disobedience or I can choose to leave. But I can never choose to not have a choice.