Piero Martinetti (1872–1943) represents one of the highest and, paradoxically, most isolated peaks of 20th-century Italian philosophical thought. A historian of philosophy and an original thinker, his figure is distinguished by an unwavering ethical integrity and a speculative depth that places him outside the dominant currents of his time, such as the neo-Hegelianism of Benedetto Croce and Giovanni Gentile. His system, known as "transcendent idealism", constitutes a unique bridge between the European rationalist tradition—with Kant, Spinoza, and Schopenhauer at its forefront—and the spiritualist metaphysics of the East, particularly the Samkhya system. The Animal Psyche, the essay by Piero Martinetti that we propose to our readers today, was the subject of a lecture given by the philosopher in 1920 at the Milanese Society for Philosophical and Religious Studies. Both in this text and in another later one, Compassion Toward Animals, Martinetti argued that animals, just like human beings, possess intellect and consciousness, and that therefore ethics must not be limited to the regulation of inter-human relations but must also necessarily extend to seeking well-being and happiness for all those sentient forms of life (i.e., those provided with a nervous system) which, like man, are capable of feeling joy and pain.