Children who have not attained the use of reason must not be obliged to swear
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic reason
Date 1274
Language English
Reference
Note Translated by Fathers of the English Dominican Province
Weblink http://www.gutenberg.org/cache/epub/19950/pg19950-images.html

Context

“as Augustine explains (De Doctr. Christ. ii) . Therefore it seems that a sacrament is not a kind of sign. Obj. 3: Further, an oath is sometimes called a sacrament: for it is written in the Decretals (Caus. xxii, qu. 5) : "Children who have not attained the use of reason must not be obliged to swear: and whoever has foresworn himself once, must no more be a witness, nor be allowed to take a sacrament," i.e. an oath. But an oath is not a kind of sign, therefore it seems that a sacrament is not a kind of sign.” source