I’m not a logician, but I believe that it is possible to start from a false premise and reach a false conclusion, and still follow all the rules. I refer you back to Hume’s fork: on one side lie logic truths, on the other side lie empirical truths. The former are deomnstrable, and the latter are not.
“I say it’s irrational to grant Marxists their basic premises”
Rationality does not depend on experience (except insofar as our rationality derives from our brains, which evolved over time, but that’s another argument). 2+2=4 with or without reference to life outside mathematics.
“What do you call people who still believe socialism can work after it has been proved a failure every time it has been tried?”
Mises maintained, time and again, that his economics was true whether or not it could be demonstrated by history. He wanted his theories to be a priori ture, or not ture at all.
Besides, any Marxist worth his salt will tell you that the reason the Soviet Union failed was because Russia had not reached the critical point of industrial development. And when you ask him why there have not been socialist revolutions in England and the U.S., for instance, he’ll tel you, “Just wait.”
It is not possible to argue with such a person; not because they are irrational, but because their rationality is locked in a closed system.
“He wanted his theories to be a priori ture, or not ture at all.”
Okay, that sounds insane. It should be: “He wanted his theories to be a priori true, or not true at all.”
sheesh, you don't think that's irrational? You are way over thinking this. The simple fact is, if your premises are flawed, then no matter how logical your cause and effect thought processes are, your conclusions cannot help but be irrational. As they say in computer programing, junk in, junk out.