Eucharistic miracle

A Eucharistic miracle is any miracle involving the Eucharist, regarding which the most prominent Christian denominations, especially the Catholic Church, teach that Christ is truly present in the Eucharist, which is by itself a Eucharistic miracle; however, this is to be distinguished from other manifestations of God. Eucharistic miracles are most known and emphasized within the context of the Catholic Church, which distinguishes between divine revelation, such as the Eucharist, and private revelation, such as Eucharistic miracles.

In general, reported Eucharistic miracles usually consist of unexplainable phenomena such as consecrated Hosts visibly transforming into myocardium tissue, being preserved for extremely long stretches of time, surviving being thrown into fire, bleeding, or even sustaining people for decades. In the modern Catholic Church, a special task-force or commission scientifically investigates supposed Eucharistic miracles before deciding whether they are "worthy of belief", in order to differentiate real Eucharistic miracles from cases of contamination by red colored microorganisms, such as Neurospora crassa or Serratia marcescens.

Scientists have advocated for using rigorous methods to detect biological impurities like microbial growth or tissue-like material in samples. As well as to provide standardized, and reproducible scientific analysis rather than relying on anecdotal or uncontrolled investigations. In an analysis of 25 events, none of the Eucharist miracles that could be investigated in such a way showed any proof for the existence of blood, human material other than single epidermal cells or erythrocytes, and may have natural explanations.

As with other private revelations, such as Marian apparitions, belief in approved miracles is not mandated by the Catholic Church, but often serves to reassure believers of God's presence or as the means to "send a message" to the population at large.

Roman Catholic Eucharistic doctrine draws upon a quasi-Aristotelian understanding of reality, in which the core substance or essential reality of a given thing is bound to, but not equivalent with, its sensible realities or accidents. In the celebration of the Eucharist, by means of the consecratory Eucharistic Prayer, the actual substance of the bread and wine are changed into the body and blood of Christ. This change in substance is not, however, the outward appearances of the bread and wine—their accidents—which remain as before. This substantial change is called transubstantiation, a term reserved to describe the change itself. Scholastic philosophical terminology was used but is not a part of the dogma that defined Christ's presence for the Roman Catholic Church at the Council of Trent. In the 13th session of 11 October 1551, it promulgated the following conciliar decree:

[I]f anyone says that the substance of bread and wine remains in the Holy Sacrament of the Eucharist together with the Body and Blood of our Lord Jesus Christ and denies that wonderful and extraordinary change of the whole substance of the wine into His blood, while only the species of bread and wine remain, a change which the Catholic Church has most fittingly called transubstantiation, let him be anathema. (Session 13, can.2).

Protestant views on the concept of Christ's presence in the Eucharist vary significantly from one denomination to another: while many, such as Lutherans, Anglicans, Methodists and the Reformed agree with Roman Catholics that Christ is really present in the Eucharist, they do not accept the definition of transubstantiation to describe it.

According to Thomas Aquinas, in the case of extraordinary Eucharistic miracles in which the appearance of the accidents are altered, this further alteration is not considered to be transubstantiation, but is a subsequent miracle that takes place for the building up of faith. Nor does the extraordinary manifestation alter or heighten the presence of Christ in the Eucharist, as the miracle does not manifest the physical presence of Christ: