If someone loses their intellect, their wudu is nullified.
The word for intellect (‘aql) has the meaning of preventing. A person’s intellect prevents him from committing a reprehensible act.
It has been narrated that if someone commits a sin, part of his intellect departs and never returns. The meaning of this is that committing a sin dims the light of a person’s faith and intellect. If he repents and performs a good deed, it will wipe out the effect of the sin but it will not make up for the loss of intellect. Had he not committed the sin in the first place, the light of his faith and intellect would have increased. Continue reading Insights into Purification: On Loss of Intellect and Sleep