Isaiah's criticism of mixing dross metals (base, cheap metals) with silver was a criticism of counterfeiting. Isaiah 1:22 lists specific sins of Israel, thereby pointing to the underlying spiritual state of the people. In context, there is no valid exegetical reason to assert that verse 22 should not be taken literally. It teaches the immorality of unbacked paper or credit money. This interpretation implies an essential unity between the actions of the people and their spiritual state; whereas another view is that their actions are only an analogy of their spiritual state, making the spiritual life of the people and their actions two distinct entities. Appeal to other passages of Scripture to illustrate this “analogical reasoning” does not necessarily prove the case in Isaiah 1:22. Ultimately, it is the context of a particular verse which must govern its interpretation. One can agree that in Jeremiah 6:28,30 the Israelites are referred to as "brass and iron" and "reprobate silver," because the context clearly warrants this. But the same is not the case in Isaiah 1:22, where Isaiah is clearly naming specific sins. Those arguing for analogy in Isaiah 1:22 are desperate to avoid the obvious conclusion: specific sins imply a violation of specific laws, which implies that men are required to obey these specific laws.
- Ian Hodge, Baptized Inflation: A Critique of “Christian” Keynesianism 87-88 (1986), at www.garynorth/freebooks.com: HTML, DjVu.