The Positive-Normative Dichotomy and Economics*
D. Wade Hands, Department of Economics
University of Puget Sound, Tacoma, WA 98416
hands@ups.edu, January 2009, Version 3.5
Paper prepared for Philosophy of Economics, Uskali Mäki (ed.), Vol. 13 of D. Gabbay, P. Thagard and J. Woods (eds.), Handbook of the Philosophy of Science. Amsterdam: Elsevier. I
There seems to be a clear distinction between the statement "I give to charity" (i.e. it is the case that I give) and the statement "I ought to give to charity" (i.e. it would be a good thing if I were to give). What is the case is one thing, a factual matter; and what ought to be the case is something else entirely, a matter of valuation, or of right and wrong. Perhaps one actually does what one ought to do, but then again, perhaps not. In either case, there does not appear to be any necessary relationship between the two types of statements; that something is the case does not imply that it should be that way, and that it should be that way does not imply that it is. The difference between “is” and “ought” seems substantive enough to be called a dichotomy: a distinction between two fundamentally different things. It is a dichotomy that we employ effortlessly in everyday life – and thus, may not appear to require philosophical analysis – but it is a dichotomy nonetheless. This is not to say of course that it is easy to determine what “is” in any particular case (What is the temperature at the center of the sun? or What is the most effective way to reduce unemployment?) nor is it always easy to know what one “ought” to do (What are the appropriate limits of tolerance? or Is lying ever the morally right thing to do?), but understanding the general conceptual difference seems to be straightforward. Even the family dog behaves as if she knows the difference between the shoe she (in fact) just chewed and the toy she ought to have chewed instead.
While the dichotomy between positive and normative – descriptive and prescriptive, facts and values, etc. – may appear straightforward, it has long been the subject of philosophical debate. Although the is-ought distinction has ancient roots in Western philosophy, much of the contemporary discussion can be traced to David Hume. For this reason it has also been called "Hume's dichotomy," "Hume's fork," and "Hume's guillotine." Hume's primary concern was to block efforts to ground ethics in the facts of nature. In his own words:
In every system of morality, which I have hitherto met with, I have always remark'd that the author proceeds for some time in the ordinary way of reasoning, and establishes the being of God, or makes observations concerning human affairs; when of a sudden I am supriz'd to find, that instead of the usual copulations of propositions, is, and, is not, I meet with no proposition that is not connected with an ought, or an ought not. This change is imperceptible; but is, however, of the last consequence. For as ought, or ought not, expresses some new relation of affirmation, 'tis necessary that it should be observ'd and explain'd; and at the same time that a reason should be given, for what seems altogether inconceivable, how this new relation can be a deduction from others, which are entirely different from it. (Hume, 1888, p. 469, emphasis in original)
The term "naturalistic fallacy" was introduced by G. E. Moore early in the 20th century for the related error of trying to (or believing that one can) derive/deduce an “ought” from an “is,” and the imperative that “one cannot deduce an ought from an is” is often considered to be the positive-normative dichotomy‟s most enduring philosophical lesson. Although this interpretation has reduced some of the controversy surrounding the dichotomy, it has not eliminated it. Even in this rather narrow imperative form, the dichotomy has been, and continues to be, much debated within the philosophical literature (Searle 1965, 2001). But the focus here is not purely philosophical debates, it is on how the positive-normative dichotomy has been interpreted within the economics literature, and it is to that topic we now turn.
HUME on MIRACLES:
No testimony is sufficient to establish a miracle, unless the testimony be of such a kind, that its falsehood would be more miraculous, than the fact, which it endeavours to establish; and even in that case there is a mutual destruction of arguments, and the superior only gives us an assurance suitable to that degree of force, which remains, after deducting the inferior
Hume entertains the possibility of a purely anomalous miracle involving a “total darkness over the whole earth for eight days” in part two of his argument. Let us quote the relevant passage.
Thus, suppose, all authors, in all languages, agree, that, from the first of January 1600, there was a total darkness over the earth for eight days: suppose that the tradition of this extraordinary event is still strong and lively among the people: that all travelers, who return from foreign countries, bring us accounts of the same tradition, without the least variation or contradiction: it is evident, that our present philosophers, instead of doubting the fact, ought to receive it as certain, and ought to search for the causes whence it might be derived. The decay, corruption, and dissolution of nature, is an event rendered probable by so many analogies, that any phenomenon, which seems to have a tendency toward that catastrophe, comes within the reach of human testimony, if that testimony be very extensive and uniform