Leff's first major work Economic Analysis of the Law: Some Realism About Nominalism is putatively a book review of Richard Posner's Economic Analysis of the Law. In actuality it is a critique of the use of any single methodology to provide normative rules for law and morality. The article is still, today, the main critique of Posner's work and economic analysis generally and is usually read in graduate seminars on Economic Analysis (though sometimes mis-identified as the Legal Realist critique). Leff makes two fundamental proposition in SRAN: (1) that all models are only very limited views of the real world. When Posner views the world through the economic model much more is hidden than is revelaed; (2) there is no system of logic for preferring one model (e.g. economic, social, political) over another unless an axiom is inserted early on into that system of logic. Leff notes that the opening of Posner's work does just that -- inserts a proposition that rational economic behavior is to be preferred to other behavior. Leff follows his insight to its logical conclusion and notes that similarly there is no way, using logic, to prove that any particular act, no matter how horrible, is normatively wrong. Put it another way, one can never prove to another person that a particular set of behaviors is right or that a different set of behaviors is wrong. He states:
- I will put the current situation as sharply as possible: there is today no way of ‘proving’ that napalming babies is bad except by asserting it (in a louder and louder voice), or by defining it as so, early in one’s game, and then later slipping it through, in a whisper, as a conclusion.
Leff continues his critique of attempts to find normative rules in law and morality in Law and Technology: On shoring up a Void and Unspeakable Ethics, Unnatural Law. In these work Leff attempts to directly address whether a normative morality can exist without God. Leff answers the question in the negative. Leff states that absent an ultimate authority figure (i.e. God) handing down moral laws from on-high there is no reason for any person to prefer one set of behavior identified as "moral" to another. Leff terms this "the Great Sez Who." Leff states as follows in the closing of UE, UL:
- I want to believe —and so do you— in a complete, transcendent, and immanent set of propositions about right and wrong, findable rules that authoritatively and unambiguously direct us how to live righteously. I also want to believe —and so do you —in no such thing, but rather that we are wholly free, not only to choose for ourselves what we ought to do, but to decide for ourselves, individually and as a species, what we ought to be. What we want, Heaven help us, is simultaneously to be perfectly ruled and perfectly free, that is, at the same time to discover the right and good and to create it.
- All I can say is this: it looks as if we are all we have. Given what we know about ourselves, and each other, this is an extraordinarily unappetizing prospect; looking around the world, it appears that if all men are brothers, the ruling model is Cain and Abel. Neither reason, nor love, nor even terror, seems to have worked to make us “good,” and worse than that, there is no reason why any thing should. Only if ethics were something unspeakable by us could law be unnatural, and therefore unchallengeable. As things stand now, everything is up for grabs. Nevertheless:
- Napalming babies is bad.
- Starving the poor is wicked.
- Buying and selling each other is depraved.
- Those who stood up and died resisting Hitler, Stalin, Amin, and Pol Pot —and General Custer too— have earned salvation.
- Those who acquiesced deserve to be damned.
- There is in the world such a thing as evil.
- [All together now:] Sez who?
- God help us.