"The second law is an empirically validated postulate of thermodynamics" [1]
And
"Empirical evidence (also empirical data, sense experience, empirical knowledge, or the a posteriori) is a source of knowledge acquired by means of observation" [2]
So, it is a law by observation after all.
[1] http://en.wikipedia.org/wiki/Second_law_of_thermodynamics
[2] http://en.wikipedia.org/wiki/Empirical_evidence
"The second law is an empirically validated postulate of thermodynamics" [1]
And
"Empirical evidence (also empirical data, sense experience, empirical knowledge, or the a posteriori) is a source of knowledge acquired by means of observation" [2]
So, it is a law by observation after all.
[1] http://en.wikipedia.org/wiki/Second_law_of_thermodynamics
[2] http://en.wikipedia.org/wiki/Empirical_evidence