The Action Axiom, true a priori?

[Seos]

...bump...

[Christel]

""The sum or range of what has been perceived, discovered, or learned" will do."
"Precisely because it is a contentious issue I am assuming that synthetic a priori truths do exist (just that "Humans act" is not one)."

Synthetic a priori truths, if they existrd, could only be expressed in some type of language, can't they? And they can only be thought in such language, can't they? Or can they be felt, perceived by senses only?

I feel the concept of synthetic a priori truths is based on experience itself, and/or knowledge that is "learned".

I still don't "know" what exactly the importance of the axiom is for Austrian economics? I have experienced on this thread that it seems to distinguish other economic theories that are based on mathematics, but what does it intrinsically for the Austrian economic theory?