An unproductive truth is none. But there are products which cannot be weighed even in patent scales, nor brought to market.
Man is a substance clad in shadows.
You just cant predict baseball
Modern education too often covers the fingers with rings, and at the same time cuts the sinews at the wrist.
One dupe is as impossible as one twin.
Be busy in trading, receiving, and giving, for life is too good to be wasted in living.