The second edition of this well-motivated introduction to intuitionistic philosophy, logic, and understanding of the continuum is still without competitors for what it accomplishes with very few technical means. The most striking change comes in the typographical presentation of the book, whose first edition (ClarendonPress, Oxford) (1977; Zbl 0358.02032) was mimeographed from typewritten pages, now being very neatly typeset using LaT_EX. There are also substantial changes. In the author’s own words, he has “completely revised the account of Brouwer’s proof of the Bar Theorem, simplified the account of valuation systems by defining them in terms of a binary relation between finite subsets of elements rather than of a set of designated elements, and revised the treatment of generalized Beth trees and the completeness of intuitionistic first-order logic, incorporating a sketch of Friedman’s proof of the completenesess of the negation-free fragment”.