Getting the correct diagnosis as soon as possible, without unnecessary tests or trials of failed treatment, is the goal and hallmark of excellent healthcare. Clinical reasoning is central to the goal of rapidly deducing the correct clinical diagnosis whilst continuing to be safe and careful. This reasoning is also required to make optimal, patient-centred decisions afterwards.Commonplace healthcare and training are far from attaining this goal. Inability to correctly diagnose patients is often accompanied by mistakes, wastage, and sometimes allegations of medical malpractice. Some countries like the USA have great wealth and advanced technology, yet consistently have poor overall outcomes and significant medicolegal litigation. Healthcare training is fragmented and flawed, with multiple styles and approaches without any unifying, clear path for learners.This book aims to address all of those limitations.Clinical reasoning is defined in a universal, simple and practical manner for all healthcare trainees, professionals and leaders. The learning journey for this skill is described, and applies for any patient in any setting. In so doing, this method aims to accelerate the acquisition of competence, and increase the extent of achieved competence.