The courts have generally held that direct taxes are limited to taxes on people (variously called "capitation", "poll tax" or "head tax") and property. All other taxes are commonly referred to as "indirect taxes," because they tax an event, rather than a person or property "per se." What seemed to be a straightforward limitation on the power of the legislature based on the subject of the tax proved inexact and unclear when applied to an income tax, which can be arguably viewed either as a direct or an indirect tax.