THE “disparate impact” theory of discrimination is curious, ubiquitous, and mischievous.  The theory holds that when an action has a disproportionate effect on some group (racial, ethnic, gender, whatever), it can be challenged as illegal discrimination—even if there was no discriminatory intent. This is quite different from a “disparate treatnaent” lawsuit, where the plaintiff must prove that the defendant treated him worse because of a particular characteristic.