ECONOMISTS VIEW THE THREAT OF PUNISHMENT AS A GOVERNMENT CRIME TAX; IF THE THREAT BE BELIEVABLE, CRIMINALS ARE DETERRED. HOWEVER, DETERRENCE IS COMPLICATED BY CRIMINALS' WIDELY DIFFERING PERCEPTIONS OF THE THREAT, AND THE RELATIVE EFFECT OF LOSS OF REPUTATION OR LIVING STANDARD INCURRED BY IMPRISONMENT. MOREOVER, CERTAINTY OF PUNISHMENT IS DEEMED TO INCREASE DETERRENCE MORE THAN SEVERITY EXCEPT WHERE SEVERITY CONTRIBUTES TO MORAL INHIBITIONS. ALTHOUGH CRIMINALS ARE DEEMED RATIONAL AND EFFECTED BY CHANGES IN THE CRIMINAL JUSTICE SYSTEM, COMMUNICATING CHANGES TO THE PUBLIC IS DIFFICULT. EVENTS SHOW THAT CRIME INCREASES ACCOMPANY SUDDEN DECREASES IN POLICE ACTIVITY. BUT SUDDEN INCREASES IN POLICE FORCES WILL NOT DECREASE CRIME UNLESS ACCOMPANIED BY MORE ASSIDUOUS POLICING MEASURES, ALTHOUGH GREATER POLICING ACTIVITY BY ITSELF MAY DECREASE MANY TYPES OF CRIMES. INCAPACITATION, OR IMPRISONMENT, PREVENTS IMPRISONED CRIMINALS FROM REOFFENDING WHILE THEY ARE IN PRISON, BUT IT IS DIFFICULT TO SEPARATE THE EFFECTS OF INCAPACITATION AND THREAT OF PUNISHMENT. HOWEVER, THE PREVENTIVE EFFECT OF INCAPACITATION MAY BE GREATER THAN SUPPOSED. POLICYMAKERS ARE WARNED TO CONSIDER THE EFFECTS ON DETERRENCE IN GENERAL OF NEW PROGRAMS FOR CRIMINALS, AS PROGRAMS POSSIBLY HELPING A FEW OFFENDERS MAY DETRACT FROM DETERRENCE OVERALL. NOTES AND AN APPENDED COMMENTARY ARE INCLUDED. (PAP)