The Catechism of the Catholic Church explains that superstition violates the first commandment which forbids the worship of false gods.
“Superstition is the deviation of religious feeling and of the practices this feeling imposes. It can even affect the worship we offer the true God, e.g., when one attributes an importance in some way magical to certain practices otherwise lawful or necessary. To attribute the efficacy of prayers or of sacramental signs to their mere external performance, apart from the interior dispositions that they demand, is to fall into superstition" (No. 2111).
In other words, if you pray to St. Joseph and ask for his help in selling your home, this is not a superstition because you are performing a religious act (in this case, saying a prayer) with the correct interior disposition (faith in the intercession of St. Joseph). However, when you just put a statue of him upside down in the yard as a kind of "good luck charm", you are guilty of superstition because you are attributing the "power" not to St. Joseph but to the physical act of putting a statue upside down in the yard.
Just for the record, there are some sources that attribute the burying of a statue of St. Joseph to Saint Teresa of Avila, who invoked St. Joseph’s intercession in order to acquire land for new convents. Saint Teresa encouraged her companions to bury their St. Joseph medals as a symbol of devotion. Over time, instead of burying medals, people started burying statues. However, if we bury a statue because we believe it has some sort of power, we’ve crossed the line between faith and superstition.
The same thing goes for the St. Benedict Medals. I have a St. Benedict cross hanging just inside my front door, not because I believe the medal has any power, but because it reminds me to invoke St. Benedict for protection.
The Most Reverend Donald W. Montrose, Bishop of Stockton, California, explained how superstition manifests itself in our times in his pastoral letter, “Spiritual Warfare: The Occult has Demonic Influence.”
“It doesn’t matter if there are statues, holy water, crucifixes, prayers to Jesus, Mary and the saints, if there is any superstitious practice it is evil. . . . . We must be careful not to use religious medals or statues in a superstitious way.
“No medal, no statue, nor religious article has any power or luck connected with it. A medal, statue or candle is only a sign of our prayer asking the saint to intercede with God for us. All worship is given to God and to Him alone.”
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