(From http://www.fields.utoronto.ca/aboutus/jcfields/fields_medal.html http://www.fields.utoronto.ca/aboutus/jcfields/fields_medal....) The genesis of the rule

(From http://www.fields.utoronto.ca/aboutus/jcfields/fields_medal.html http://www.fields.utoronto.ca/aboutus/jcfields/fields_medal....) The genesis of the rule that it be awarded only to mathematicians no older than forty is evidently the statement that “… while it was in recognition of work already done, it was at the same time intended to be an encouragement for further achievement on the part of the recipients and a stimulus to renewed effort on the part of others”.