One of the reasons why Anthony worked so hard to convert heretics was because he genuinely felt sorry for them. He saw that they were depriving themselves of the most precious gift of the Eucharist, and he believed that no one could long survive without this spiritual nourishment.
One day, a heretic told Anthony that he would believe that Christ was truly present in the Eucharist only if his mule bowed down to it.
They established that the test should take place in three days. The heretic starved his mule for the next three days. When the appointed time had arrived, Anthony stood off to one side with the consecrated host in his hands, while the heretic stood to the other holding some fodder for the mule to eat. The mule, ignoring its own extreme hunger, went before the Eucharist and knelt down to adore the Blessed Sacrament.
There are many other miracles associated with Anthony’s ministry, but they should not distract our attention from the fact that most of Anthony’s ministry was performed in simple everyday ways. It was his fervent life style, his prayer, his gentleness, his humble use of his great learning that brought people to conversion. Anthony also ministered to those ministering to others, for he taught theology to the friars in Bologna, Montpellier, Toulouse and Padua. This work and his writings earned him the title of Evangelical Doctor of the Church.