This book argues that the shift in general equilibrium theory, from its early long-period to the modern very-short-period versions, has had very important consequences which are insufficiently appreciated by large parts of the economics profession. This shift has produced new difficulties, and has undermined central tenets of neoclassical macroeconomic theory (such as the negative dependence of aggregate investment on the interest rate, or the existence of a downward-sloping demand curve for labour) which had their basis in the long-period versions where capital was treated as a single factor. According to the author, what makes it difficult to appreciate these consequences is the current imperfect grasp of the long-period method (an approach common to classical and to the first generations of neoclassical economists, but nowadays often confused with steady-growth analysis). The origins of this problem date back to the 1930s, and to this day still obscure the history and the logic of the neoclassical approach. The book explains the analytical differences between long- period, steady-growth, and short-period general equilibrium analyses, and proves that on this basis considerable clarification can be achieved, not only in many aspects of the history of economic theory, but also in fundamental issues in the theories of value, distribution, capital, investment, employment and money. For example, the reasons for the disagreements in the #Cambridge controversies# over capital theory become very apparent. This stimulating critique on the present state of economic theory will appeal to academics and researchers with an interest in macroeconomics, the history of economic thought, and the theory of value and distribution. It will also enlighten and inform anyone wanting to understand the reasons behind the current dissatisfaction with neoclassical economics.