In spite of the commonly held opinion according to which Galen's authority was gradually superseded by Vesalius and his followers, a close look at the influence that Galen's psychological works exerted on physicians and philosophers of the early modern period reveals quite a different picture. Not only were Galenists often keen to embrace the new anatomical discoveries, eventually they even contributed to shaping a series of new analytical, practical and experimental tools that started an in-depth transformation of the traditional rationale, with far-reaching and unexpected consequences in domains such as theory of matter, philosophical anthropology and medical experimentation. Through the lens provided by mental disease and its connection to the soul, a new concept of the body and the human animal ultimately emerges: a concept that accompanies the development of early modern ideas on subjectivity and the self.