Book excerpt: Focusing on nonprofits' growing dependence on public funding, their tendency toward political polarization, their often idiosyncratic missions, and their increasing commercialism, Peter Frumkin argues that the long-term challenges facing nonprofit organizations will be solved only when they achieve greater balance among their four central functions. Probing foundational thinking as well as emergent ideas, the book is an essential guide for nonprofit novices and experts alike who want to understand the issues propelling public debate about the future of their sector.