"One cannot Sell without at the same instant and in the same act Buying, nor Buy anything without simultaneously Selling something else..." #QotD

"A market for Products is products in Market. The fundamental thus tersely expressed may be formulated more at length in this way: One cannot Sell without at the same instant and in the same act Buying, nor Buy anything without simultaneously Selling something else; because in Buying one pays for what he buys, which is Selling, and in Selling one must take pay for what is sold, which is Buying. As these universal actions among men are always voluntary, there must be also an universal motive leading up to them; this motive on the part of both parties to each and every Sale can be no other than the mutual satisfaction derivable to both; the inference, accordingly, is easy and invincible, that governmental restrictions on Sales, or prohibitions of them, must lessen the satisfactions and retard the progress of mankind."

~ Arthur Latham Perry, from his best-selling Principles of Political Economy (1891)