A lawyer may have a great many important cases, but he has only one at a time; that is, he _attends_ to but one at a time.

The one may be intricate, involving many facts, and requiring to be examined in many aspects and relations.

But he looks at but few of these facts and regards but few of these relations at a time.

The points which demand his attention come one after another in regular succession.

His mind may thus be kept calm.