レオンチェフが、1970年末の第83回経済学会で行った表題の会長講演(原題は「Theoretical Assumptions and Nonobserved Facts」)で、次のようなことを述べている(Mostly Economics経由のLars Syll経由)。

Much of current academic teaching and research has been criticized for its lack of relevance, that is, of immediate practical impact. ...I submit that the consistently indifferent performance in practical applications is in fact a symptom of a fundamental imbalance in the present state of our discipline. The weak and all too slowly growing empirical foundation clearly cannot support the proliferating superstructure of pure, or should I say, speculative economic theory.
...Uncritical enthusiasm for mathematical formulation tends often to conceal the ephemeral substantive content of the argument behind the formidable front of algebraic signs.
In the presentation of a new model, attention nowadays is usually centered on a step-by-step derivation of its formal properties. But if the author — or at least the referee who recommended the manuscript for publication — is technically competent, such mathematical manipulations, however long and intricate, can even without further checking be accepted as correct. Nevertheless, they are usually spelled out at great length. By the time it comes to interpretation of the substantive conclusions, the assumptions on which the model has been based are easily forgotten. But it is precisely the empirical validity of these assumptions on which the usefulness of the entire exercise depends.
What is really needed, in most cases, is a very difficult and seldom very neat assessment and verification of these assumptions in terms of observed facts. Here mathematics cannot help and because of this, the interest and enthusiasm of the model builder suddenly begins to flag: “If you do not like my set of assumptions, give me another and I will gladly make you another model; have your pick.” ...
To sum up with the words of a recent president of the Econometric Society, " . . . the achievements of economic theory in the last two decades are both impressive and in many ways beautiful. But it cannot be denied that there is something scandalous in the spectacle of so many people refining the analysis of economic states which they give no reason to suppose will ever, or have ever, come about. . . . It is an unsatisfactory and slightly dishonest state of affairs."
But shouldn’t this harsh judgment be suspended in the face of the impressive volume of econometric work? The answer is decidedly no. This work can be in general characterized as an attempt to compensate for the glaring weakness of the data base available to us by the widest possible use of more and more sophisticated statistical techniques. Alongside the mounting pile of elaborate theoretical models we see a fast-growing stock of equally intricate statistical tools. These are intended to stretch to the limit the meager supply of facts.
Since, as I said before, the publishers' referees do a competent job, most model-testing kits described in professional journals are internally consistent. However, like the economic models they are supposed to implement, the validity of these statistical tools depends itself on the acceptance of certain convenient assumptions pertaining to stochastic properties of the phenomena which the particular models are intended to explain; assumptions that can be seldom verified.


だがこの厳しい審判は、計量経済分析の研究が大量に存在することを考えると留保すべきではないか? その答えは、きっぱりと否、である。そうした研究は、我々が利用できるデータベースの明白な貧弱さを、ますます洗練化された統計的技法を目一杯駆使することによって補う、という試みとして概ね特徴付けられる。精緻な理論モデルが積み重なっていくのと並行して、同じくらい複雑な統計的ツールが急速に積み上がっていくのを我々は目にしている。それは、事実の供給が乏しいことからくる限界を押し広げることを意図している。