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