Foreword / G. C. Harcourt -- Pt. I. Overview -- 1. Introduction -- 2. An overview of concepts and approaches -- Pt. II. Theoretical Issues -- 3. Intellectual ancestors: Irving Fisher and Maynard Keynes -- 4. Accelerator theory -- 5. Jorgenson's model of investment -- 6. The limitations of Jorgenson's model -- 7. Putty-clay models of investment -- 8. Adjustment costs and q theory -- 9. Uncertainty and investment -- 10. Post Keynesian analyses of investment -- Pt. III. Testing the Theories -- 11. Comparing Jorgenson's model and accelerator theory: evidence from the UK -- 12. Uncertainty in competing models of investment: evidence from the USA -- Pt. IV. Empirical Applications of Investment Principles -- 13. Computing investment in the New Economy: US evidence -- 14. Investment and development: a cross-sectional analysis -- 15. Residential investment: bubbles and crashes in the UK housing market, 1980-99 -- Pt. V. Conclusion -- 16. Concluding remarks.