In 1503, Nifo published De intellectu, the major work of his early career, touching on questions of philosophical psychology. Based on a detailed assessment of the views of his predecessors, Nifo in this work presented an analysis of the main issues of Peripatetic noetics, namely origin and immortality of the intellect or rational soul, its relation to the body, its unity and parts, the speculative intellect, and intellectual beatitude. Here the 1554 edition is reproduced. The Introduction is followed by an extensive analytical summary of the contents of the work. The Appendix contains a chronology of Nifo’s life and works, and a full index of the chapters of De intellectu.