church until quite late in life, there is a genre of tales of deathbed conversions. Biographers usually doubt these, though the baptism of James K. Polk is well documented. Personal beliefs The inner beliefs of the presidents are much more difficult to establish than church membership. While some presidents have been relatively open about religion, many have been reticent to the point of complete obscurity. Researchers have tried to draw conclusions from patterns of churchgoing or religious references in political speeches. When explicit statements are absent, it is difficult to assess whether the presidents in question were irreligious, were unorthodox in their beliefs, or simply believed that religion was not a matter for public revelation. On the other hand, there are several presidents who considered themselves aligned with a particular church, but who withheld from formal affiliation for a time. James Buchanan, for instance, held himself allied with the Presbyterian church, but refrained from joining it until he left office. Some presidents changed their beliefs and affiliation at some point in their lives; synthesis of statements and membership from different periods can be misleading. Deism and the Founding Fathers Deism was a religious philosophy in common currency in colonial times, and some Founding Fathers (most notably Thomas Paine, who was an explicit proponent of it, and Benjamin Franklin, who spoke of it in his Autobiography) are identified more or less with this system. Thomas Jefferson became a deist in later life, and Washington, James Madison, James Monroe, and John Tyler are often identified as having some degree of deistic beliefs. Unitarianism and Nontrinitarianism Four presidents are affiliated with Unitarian churches, and a fifth (Jefferson) was an exponent of ideas now commonly associated with Unitarianism. Unitarians fall outside of Trinitarian Christianity, and the question arises as to the degree to which the presidents themselves held Christian precepts. The information is generally available in the statements of the presidents themselves; for example, John Quincy Adams left detailed statements of his beliefs. William Howard Taft, a Unitarian, is noted to have said in a letter to a friend, "I am interested in the spread of Christian civilization, but to go into a dogmatic discussion of creed I will not do whether I am defeated or not. ... If the American electorate is so narrow as not to elect a Unitarian, well and good. I can stand it." Two presidents were Quakers (Herbert Hoover