Human uses of mammals that "one is well advised to study the behaviour rather than attempting to get at any underlying emotion". Charles Darwin however had accepted the idea of emotion in animals, writing his 1872 book "The Expression of the Emotions in Man and Animals" on the subject. Darwin believed that mammals had social, mental and moral lives. In "The Descent of Man" (1871), he wrote: "There is no fundamental difference between man and the higher mammals in their mental faculties." Biologists remained wary of the idea, even for the great apes, but this led to serious difficulties, as Donald O. Hebb explained
The Sacrament of the Body and Blood of Christ—Against the Fanatics the Sacrament of the Altar with the correct one. Zwingli wrote that he was not placing reason over the Scriptures, but instead properly distinguishing between the human and divine natures of Christ. Since Christ's human nature could not participate in the omnipresent attribute of the divine nature, his body and blood could not be truly present in the bread and wine. Luther's characterization of him as placing reason over Scripture was therefore a straw-man argument. Luther's custom of referring to those who opposed him in non-Christian terms in "The Sacrament of the Body and Blood of Christ" sounds unusual to