The inner beliefs of the presidents are much more difficult to establish than church membership. While some presidents have been relatively voluble 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.