Logic with Trees is a new and original introduction to modern formal logic. Preferring explanation and argument to intimidatingly rigorous development, Colin Howson presents the formal material in a clear and informal style that both beginners and those with some knowledge of formal methods will appreciate. Examples and exercises guide readers through the book, and answers to selected exercises at the end allow them to monitor their own progress. Howson covers all the key methods in both truth-functional and full first order logic using the truth-tree, or semantic tableau, approach throughout. In addition, he discusses alternative deductive systems, transfinite numbers and the famous theorems of Godel and Church, and he concludes with an analysis of the liar paradox and of the weaknesses of the truth-functional account of conditionals. Logic with Trees will be particularly useful for those who feel wary of formal methods, as it shows how simple even quite sophisticated formal reasoning can be. It offers an indispensable introduction to logic for students of philosophy, mathematics and computer science.