 Brentano always emphasized that he meant to teach his students to think critically and in a scientific manner, without holding prejudices and paying undue respect to philosophical schools or traditions. When former students of his took a critical approach to his own work, however, when they criticized some of his doctrines and modified others to adapt them for their own goals, Brentano reacted bitterly. He often refused to discuss criticism, ignored improvements, and thus became more and more isolated, a development that was reinforced by his increasing blindness.