There is an interesting perspective on whether Outside Money can serve as the essence of "money": it is widely accepted not because of legal definitions, but because it functions as collateral—when liquidity is tight, it can be "produced" into real currency.

This idea essentially reflects the logic of the repurchase agreement market. The entire operation of the repo market revolves around collateral. In other words, collateral is the true center of the game.

Looking at it in the context of the old international financial order—the era of the Bretton Woods system and US dollar global dominance—this collateral framework becomes especially critical. During that period, whoever controlled high-quality collateral held the power over financial pricing.