The corruptible body is a load upon the soul, because it hinders the use of reason even in those matters which belong to man at all ages.
 Thomas Aquinas, Summa Theologica (1274). copy citation

add
Author Thomas Aquinas
Source Summa Theologica
Topic age reason
Date 1274
Language English
Reference
Note Translated by Fathers of the English Dominican Province
Weblink http://www.gutenberg.org/cache/epub/17611/pg17611-images.html

Context

“Therefore, in the state of innocence, children would not have had the perfect use of reason, which they would have enjoyed later on in life. Yet they would have had a more perfect use than they have now, as to matters regarding that particular state, as explained above regarding the use of their limbs (Q. 99, A. 1) . Reply Obj. 1: The corruptible body is a load upon the soul, because it hinders the use of reason even in those matters which belong to man at all ages. Reply Obj. 2: Even other animals have not at birth such a perfect use of their natural powers as they have later on. This is clear from the fact that birds teach their young to fly; and the like may be observed in other animals.” source