There is much less enthusiasm about formal logic among ordinary educated people today than there was a few short centuries ago, in the period roughly from Peter Abelard to Leibniz, when logic seemed as if it might be developed into a machine for producing unlimited numbers of true and valuable propositions. But the less glorious role to which Bertrand Russell consigned it — helping us avoid false inferences — is still a useful one. By stripping away the particulars from an argument, particulars which may have such emotional force as to blind us to otherwise evident fallacies, the reduction of an argument to its purely logical form can act as a form of error-checking.

Take, for example, my blog-buddy Jo, the Democratic Veteran. Asked if

>Some X does not have quality Y.

>Therefore, no X has quality Y.

represented a valid inference, Jo would presumably say, “Heck, no! Perhaps some, but not all, X has quality Y.”

But commenting on my tentative support for the RAVE Act (as expressed here, Jo writes as follows:

Mark argues that the law might have a chance of measurably reducing Ecstasy/MDMA use, but I disagree. If just passing a law worked, we would be a nation of tea-totalers, the death rows in this country would be empty and no one would ever drink and drive. Neither would I ever have had to stand with any of my troops who had flunked a urinalysis for some drug or another at Captains Mast.

which, if I read it correctly, makes the argument that since some people aren’t deterred, no one is deterred.

I doubt that Aristotle or William of Ockham would have approved of the logical structure of that argument. What either of them would have thought of the RAVE Act is a different matter, as is the question, which I regard as still open, whether the RAVE Act is on balance good legislation.

Author: Mark Kleiman

Professor of Public Policy at the NYU Marron Institute for Urban Management and editor of the Journal of Drug Policy Analysis. Teaches about the methods of policy analysis about drug abuse control and crime control policy, working out the implications of two principles: that swift and certain sanctions don't have to be severe to be effective, and that well-designed threats usually don't have to be carried out. Books: Drugs and Drug Policy: What Everyone Needs to Know (with Jonathan Caulkins and Angela Hawken) When Brute Force Fails: How to Have Less Crime and Less Punishment (Princeton, 2009; named one of the "books of the year" by The Economist Against Excess: Drug Policy for Results (Basic, 1993) Marijuana: Costs of Abuse, Costs of Control (Greenwood, 1989) UCLA Homepage Curriculum Vitae Contact: