Why is there a cross on the altar in some churches?
Pope Francis spoke about it very concisely in this past Wednesday’s General Audience:
On the table there is a cross to indicate that on this altar what is offered is the sacrifice of Christ.
This is what liturgical law has to say about it, in the General Instruction of the Roman Missal, # 308:
Likewise, either on the altar or near it, there is to be a cross, with the figure of Christ crucified upon it, a cross clearly visible to the assembled people. It is desirable that such a cross should remain near the altar even outside of liturgical celebrations, so as to call to mind for the faithful the saving Passion of the Lord.
Obviously it leaves room for alternative practices, and so we don’t see the crucifix on the altar in every Catholic church we visit – and this is not wrong. Even still, the altar cross has been more frequently seen since the papacy of Benedict XVI. The Papal Master of Ceremonies, Msgr. Guido Marini, explains why it might be better to have the cross in the center, on the altar, and indeed, why Benedict XVI promoted this practice, of which Pope Francis evidently also approves:
The centrality of the crucifix in the celebration of divine worship was more evident in the past, when the normative custom was that both priests and faithful would turn and face the crucifix during the eucharistic celebration. The cross was placed in the center above the altar, which in turn was attached to the wall, according to the norm. For the present custom of celebrating the Eucharist “facing the people,” often the crucifix is located to the side of the altar, thus losing its central position.
Then-theologian and Cardinal Joseph Ratzinger many times had underscored that, even during the celebration “facing the people,” the crucifix should maintain its central position, and that it would be impossible to think that the depiction of the Crucified Lord – which expresses his Sacrifice and therefore the most important significance of the Eucharist – could be in some way a source of disturbance. Having become Pope, Benedict XVI, in the preface to the first volume of his [Collected Works], said that he was happy about the fact that the proposal he had advanced in his celebrated essay, The Spirit of the Liturgy, was making headway. That proposal consisted in the suggestion that: “Where a direct common turning toward the east is not possible, the cross can serve as the interior ‘east’ of faith. It should stand in the middle of the altar and be the common point of focus for both priest and praying community.”