The unifying theme of these thirteen essays is understanding. What is it? What does it take to have it? What does it presuppose in what can be understood? In the first group of essays, John Haugeland addresses mind and intelligence. Intelligibility comes to the fore in a set of “metaphysical” pieces on analog and digital systems and supervenience. In the third set of papers, Haugeland elaborates and then undermines a battery of common presuppositions about the foundational notions of intentionality and representation. Finally, the fourth and most recent group of essays confronts the essential character of understanding in relation to what is understood. The necessary interdependence between personality and intelligence is developed and explained, specifically in the conditions of the possibility of objective scientific knowledge.