Congress was never designed for the world it now governs. Across two centuries, the institution has drifted into a role it no longer understands, trapped between public expectation and the silent machinery of the administrative state. The Diagnostic Republic is a structural examination of that drift - and a blueprint for reclaiming democratic self‑governance. From the rituals of hiring and firing to the hidden architecture of law enforcement, from the cognitive demands of representation to the palimpsest of forgotten statutes, this book reveals how a modern republic loses sight of itself - and how it can learn to see again. Clear, unsentimental, and architecturally precise, this is a guide for citizens who want to understand the machinery beneath their democracy, and for leaders who must learn to maintain the institutions they inherit. A republic cannot survive on sentiment alone. It must know how it works.