Consolidation Principle

The need to exchange from one coin in order to trade with merchants of another is a cost. This cost must be non-zero even if automated, as it must consume space and/or time. As such one coin is always "better" (higher utility) than two.

We can reasonably assume that two distinct moneys cannot perpetually have identical utility. Thier's Law discusses the consequences of better money in the absence of state controls. From this we necessarily conclude that the better of the two monies will eventually replace the other, and that this will be the case for all coins in the absence of state controls.

This does not imply that new coins cannot be created or exist over a significant amount of time. It implies that there is a market pressure toward a single coin.