i think what they mean by alchemy's FIRST law of equivalent exchange means that that specific law is the basis of Alchemy. It is, if you will, the most important law, thus given the name 'First' Law. ack! i'm confusing myself, in a nutshell, the word "FIRST" is just there to emphasize that "toukakoukan" is the most important law in Alchemy. there we go.
the japanese by itself flows well, and sounds freaking awesome, even though i don't understand it. but whatever. what i was comparing the dub to was just the fan-translations.
In those days, we really believed that to be the world's one and only truth.