The donative theory is theoretically superior to other theories of the charitable tax exemption in explaining not only the core concept of what is a charity but also the major limits on the charitable status under both federal and state tax law. Nevertheless, the most theoretically elegant theories can fail in the face of insurmountable problems of practical implementation. Since 1954, the Internal Revenue Code has distinguished between certain types of charitable entities for purposes of limiting the deductibility of charitable gifts. As originally enacted, § 170 generally limited the deduction for charitable donations to 20% of the taxpayer's adjusted gross income; however, donations to churches, certain educational institutions, and hospitals were permitted up to 30%. Analysis of the practical aspects of implementing the donative theory must begin with the relationship between the tax exemption and the level of public support necessary to invoke exemption.