Paul VI felt very strongly that certain theological currents were threatening several Catholic doctrines and practices including:
Pope Paul VI in the opening of the letter declares the following teachings are impermissible:
"These and similar opinions do great harm to the faith and devotion to the Divine Eucharist. And therefore, so that the hope aroused by the Council, that a flourishing of Eucharistic piety which is now pervading the whole Church, be not frustrated by this spread of false opinions"