Trade: What it is
If I have traded my fish for your corn, the following five things must be true:
a) I intended that you get the rights to my fish, on condition that I get the rights to your corn.
b) You intended that I get the rights to your corn, on condition that you get the rights to my fish.
c) I consent to your conditions in (b), and you know it.
d) You consent to my conditions in (a), and I know it.
e) Because of a-d, we achieve our intentions in (in a and b).