I never said that history and original intent shouldn’t be considered at all. They certainly should enter into the equation of how we interpreter the Constitution, but that doesn’t mean they are the only players in the game or even the most important players. Original intention as gleaned from the circumstances of the writers is something that is a persuasive authority, meaning that it carries weight, but doesn’t in and of itself settle the matter.
The missing ingredient here that makes it all work is a principle called "Stare Decisis’ which literally means “let the decision stand.” This principle is core to the legal reasoning of common law countries like the united states. Briefly stated, it means that when an appellate court (Like the US Supreme Court) decides a case and issues a written majority opinion on the case, the ratio decendi (the core reasoning of the decision) is considered binding law within that court’s jurisdiction. This principle is also called the principle of precedent.
Precedent, unlike other legal authorities, is considered to be a binding authority rather than one that is merely persuasive, and in large measure is what stops American Constitutional law from completely falling to pieces. Other countries in which precedent isn’t a binding authority (called civil law countries as opposed to common law which the U.S. is) need to have very explicit documents in order to prevent the courts from falling into chaos. For example, the German Constitution is a massive 134 pages long, which is enormous compared to the U.S. Constitution of only about 4500 words. We can get away with a short one that mentions core freedoms and concepts without explaining them in detail because we have a court system that has the power to give legally binding interpretations of it.
It is the use of the binding authority of precedent and the text of the constitution itself combined with the many types of persuasive authorities that make our system work and stop the Constitution from unraveling.