...as conceived by austrians? I think that it is proved by assuming that the next good in a series is valued at more than the preceeding ones and from that you derive the contradiction that exchanges wouldn't take place because there could not be a time when the value to be gained is greater than the value to be lost -subjectively.
Then again, my explaination seems circular on second thought due to the "subjectively" qualification.
The fact is I am woefully uneducated about the exact, logical, reason behind the austrian marginal theory and I've never read anything that explains it in the context of austrian tradition.
It is true merely by thinking about it;
Why would anyone buy anything if they didn't value the good higher than the money spent?
Why would anyone sell anything if they didn't value the money gained higher than the good?
In that you have it; the value of the good is different to those two people, and hence the value is subjective. Obviously there are numerous other examples.
The difference between libertarianism and socialism is that libertarians will tolerate the existence of a socialist community, but socialists can't tolerate a libertarian community.
Equally; do you have anything which you think is great and others think is awful. Any music you love and others don't. Any films you love which others can't stand?
It merely states that one will aim to satisfy their most urgent preferences first, second-most urgent next etc. It's a matter of logic. The "subjectively" isn't circular. All value resides in the an agent perceives an object's ability to alleviate their wants.
Freedom of markets is positively correlated with the degree of evolution in any society...
thedesolateone gave some great short answers.
for a beefier version http://mises.org/etexts/menger/three.asp
carl menger , principles of economics
Where there is no property there is no justice; a proposition as certain as any demonstration in Euclid
Fools! not to see that what they madly desire would be a calamity to them as no hands but their own could bring