Mystici Corporis Christi §78

⁷⁸ For indeed We are not ignorant of the fact that his profound truth - of our union with the Divine Redeemer and in particular of the indwelling of the Holy spirit in our souls - is shrouded in darkness by many a veil that impedes our power to understand and explain it, both because of the hidden nature of the doctrine itself, and of the limitations of our human intellect. But We know, too, that from well-directed and earnest study of this doctrine, and from the clash of diverse opinions and the discussion thereof, provided that these are regulated by the love of truth and by due submission to the Church, much light will be gained, which, in its turn will help to progress in kindred sacred sciences. Hence, We do not censure those who in various ways, and with diverse reasonings make every effort to understand and to clarify the mystery of this our wonderful union with Christ. But let all agree uncompromisingly on this, if they would not err from truth and from the orthodox teaching of the Church: to reject every kind of mystic union by which the faithful of Christ should in any way pass beyond the sphere of creatures and wrongly enter the divine, were it only to the extent of appropriating to themselves as their own but one single attribute of the eternal Godhead. And, moreover, let all hold this as certain truth, that all these activities are common to the most Blessed Trinity, insofar as they have God as supreme efficient cause.