Catholics often cite the wedding at Cana as proof that Mary has unique persuasive power with Jesus — since He told her His time had not yet come, yet still performed the miracle. But if that single incident establishes Mary as an eternal intercessor, then by the same logic we could also pray to the Syrophoenician woman, because her persistence likewise moved Jesus to act outside His original mission (Mark 7:25–29).
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Yes — the Catholic Church does encourage praying to saints for intercession.
Saints are friends of God who are already in Heaven. Because they are united with God, their prayers are considered especially powerful.
Is it in modern business talks and negotiations would go easier if arranged by a friend of both parties?