The reader considers the problems, styles, works and phases proper to Leibnizian philosophy. In point of fact it presents excerpts from every important juncture of Leibniz's work, grasping the coherence of it and the metaphysical horizon. The reader is structured around four major problems: 1. one and many; 2. the individual; 3. evil; 4. logic. 1. The concept of one and many is common to all philosophy since Parmenides but Leibniz recasts the notion in a modern light: it's a matter of grasping the fundamental unity of the Real despite its diversity. This unity can be understood either as a whole, consisting of a single world, consistent and coherent despite the constant changes occurring in it, or as a monad -- the metaphysical equivalent to the number one -- which represents the smallest building block of everything. 2. Consideration of the one and the many permits an analysis of the individual's status as a being, simultaneously one and many. The individual exists in various ways and on various levels: as an aggregate of matter, as life, as a person or as a conscience. But in all these guises, it expresses a unique point of view as regards the universe. 3. There remains a sticking point: human beings conceive of the Many as evil. And multiplicity is indeed akin to disorder, to the breakdown of essential cohesion, to noise, to the irrational. How is the Creator's bounty to be saved? Theodicy provides the key to this theological, moral and physical problem of evil by contemplating the idea and the origins of the world. 4. Finally, reflecting on the Real evokes the reason -- human or divine -- which characterizes the thought processes of the Real, and the language in which it expresses its understanding of the one and the many. It is then worthwhile to lay out a set of logical principles underlying a rationality capable of taking in the root causes of all things.