We all make decisions, sometimes dozens in the course of a day. This paper is about what is involved in this activity. It's my contention that the ability to deliberate, to weigh different courses of action, and then to decide on one of them, is a distinctively human activity, or at least an activity which sets man and the higher animals apart from other creatures. It is as much decisio as ratio that constitutes the distinguishing mark of human beings. Homo (...) may not always be rationalis, but he is always decidens.The paper is about practical decision, although there is also another important kind of decision that I won't discuss, namely cognitive decision. The difference is roughly that which distinguishes the function of a jury from that of a judge, at least in jury trials. The jury's job is to arrive at an answer to the question: guilty or not guilty? This is a cognitive decision, a decision that, on the basis of the evidence, such-and-such is the case. The judge, apprized of the jury's cognitive decision, makes the practical decision to sentence the guilty party to 20 years. On some other occasion, I hope to be able to say something about cognitive decision, as well as about a third kind of decision named value decision. (shrink)