Introduction

The 30 different contributions forming this volume have been arranged into eight major parts. The ‘Prelude’, contains two contributions. There is my contribution ‘Computable and constructive economics, undecidable dynamics and algorithmic rationality: an essay in honour of Professor Kumaraswamy (Vela) Velupillai’ (Chapter 1) where I try to give a sketch of Velupillai’s intellectual path. Here I focus on Velupillai’s works on the Stockholm school, on phenomenological dynamics, on constructive and computable economics and algorithmic social sciences. Great emphasis is posed on the constructive and computability elements of his research which leads both to negative results (for example the uncomputability of Walrasian general equilibrium and of the first and second welfare theorems) and positive ones like the definition of the Keynes-Simon-Velupillai rationality. That is a concept of rational behaviour which does not imply Olympic capacities on the part of human agents. This provides new foundations for Simon’s behavioural economics. The second chapter, ‘From an admirer and a friend’ (Chapter 2), is a short letter from Robert Clower. This is a cameo expressing the appreciation of a great economist to another great one; Clower has made very important contributions to economics with respect to rational decision making and to the functioning of the economic systems as a whole. In a way his previous work links well with the work of Velupillai on phenomenological Keynesian dynamics and on the foundations of computable economics. Several of Velupillai’s works are based on Clower’s contributions. The letter is a homage from Clower to Velupillai. Velupillai was criticized for having published in his edited volume in honour of Richard Goodwin (Velupillai 1989) a short letter from Kenneth Galbraith. I also wish to be criticized for having done a similar thing. I thank Clower for having given the permission to publish his letter. Part II, ‘Dynamical systems, business cycles and macroeconomics’ contains the contributions of three great macroeconomists: Paul Samuelson, Robert Solow and Axel Leijonhufvud, who each in their own way deals with issues related with phenomenological macroeconomic dynamics. In ‘The Richard Goodwin circle at Harvard (1938-1950)’ (Chapter 3) Paul Samuelson pays a homage to Velupillai by providing recollections of his mentor at Harvard. This chapter gives a glimpse of what Harvard was in the 1940s and

1950s. Personal recollections involve scholars of the calibre of Schumpeter, Leontief, Haberler, Hansen. Samuelson’s writings are always full of content and of elements for future reflections or elaborations. The reading of this contribution is a breath of fresh air. From the point of view of the birth and development of phenomenological macrodynamics Samuelson gives an important credit to Richard Goodwin’s importance – in a way also supporting Velupillai’s work on Goodwin’s one-sided oscillator. He concludes his contribution in this volume with the following:

Just as John Hicks gained much from talking to Harrod, Meade and whomever about Keynesian matters, in my recollection much of what ended up in Hick’s 1950 A Contribution to the Theory of the Trade Cycle would not have been possible if he had not earlier talked over those issues with Dick Goodwin. That’s the way the dynamics of scientific discovery works. Bees take elsewhere my honey; and much of what is ‘mine’ was brought to me by those same busy bees. Insiders know these things. But historians never can get things perfectly right.