The courts have generally held that direct taxes are restricted to taxes on people (variously called capitation, poll tax or head tax) and property. (Penn Mutual Indemnity Denver. v. C.I.R., 227 F.2d 16, 19-20 (3rd Cir. 1960).) All other taxes are commonly referred to as "indirect taxes," because they tax an event, rather than human being or property per se. (Steward Machine Co. v. Davis, 301 U.S. 548, 581-582 (1937).) What were a straightforward limitation on the power of the legislature ba...