On the subject of Validity of the Holy Sacrifice of the Mass

There are three parts to a sacrament that pertain to its being valid, 1) Form, 2) Matter, and 3) Intention.

According to Pope Leo XIII from Apostolicae Curae,

"In the examination of any rite for the effecting and administering of Sacraments, distinction is rightly made between the part which is ceremonial and that which is essential, the latter being usually called the "matter and form". All know that the Sacraments of the New Law, as sensible and efficient signs of invisible grace, ought both to signify the grace which they effect, and effect the grace which they signify."

Pope Leo XIII continues discussing the necessary intention,

"With this inherent defect of "form" is joined the defect of intention" which is equally essential to the Sacrament. The Church does not judge about the mind and intention, in so far as it is something by its nature internal; but in so far as it is manifested externally she is bound to judge concerning it. A person who has correctly and seriously used the requisite matter and form to effect and confer a sacrament is presumed for that very reason to have intended to do (intendisse) what the Church does."

Although in Apostolicae Curae, the Pope is addressing specifically the sacrament of Holy Orders (a subject I hope to address soon). The parts of a valid sacrament are the same for all sacraments; it is necessary to maintain what has essentially passed on from Christ and the Apostles. The Form are the words of the sacrament being administered. In regards the Holy Sacrifice of the Mass, the form for the Holy Eucharist is "Hoc est enim corpvs mevm" (This is my body) and "Hic est enim calix sangvinis mei, novi et aeterni testimenti, mysterivm fidei, qvi pro vobis et pro mvltis effvndetvr in remissionem peccatorvm" (This is the chalice of my blood, the new and eternal testament, which for you (pl.) and for many is poured out in remission of sin). Any deviation from these essential words should be considered doubtful, especially if a different meaning is specified or intended, I.E. if the words do not "signify the grace which they effect, and effect the grace which they signify." Usually, the words of consecration which are most regularly challenged come from those (mis)spoken over the chalice: for many v. for all and the mystery of faith.

In a simple manner, we can look to the Catechism of the Council of Trent which explains, "With reason, therefore, were the words 'for all' not used, as in this place the fruits of the Passion are alone spoken of, and to the elect only did His Passion bring the fruit of salvation." The use of the words "for all" signify quite something else altogether. Clearly "for all" signifies salvation even for those who reject and/or do not believe; please remember that "extra ecclesiam nvlla salvs," that-is, outside the Church, there is no salvation. This is a solid dogma of the Church (about which I also hope to write soon). Regarding the words "Mysterivm Fidei" (Mystery of Faith) this same Catechism explains their necessity for they "signify that what lies hidden, and concealed and far removed from the perception of the eye, is to be believed with a firm faith." Pope Innocent III explains the necessity of these words in the sacramental form of the Holy Eucharist as as such, because they explicitly protect against the error of disbelief. It is the "mystrium fidei" which declares the True Presence of Christ upon Catholic altars.

These same pronouncements from the teachings of the Popes are repeated in the Papal Bull de Defectibus of Pope St. Pius V. This bull was published in the front of every altar missal until the publication of the Novus Ordo Missae, when the first (IMHO dolorous) changes were made to the sacraments to conform to the "modern mind." Harken to the words of Pope St. Pius V:

"The priest who is to celebrate Mass should take every precaution to make sure that none of the things required for celebrating the Sacrament of the Eucharist is missing. A defect may occur with regard to the matter to be consecrated, with regard to the form to be observed and with regard to the consecrating minister. There is no Sacrament if any of these is missing: the proper matter, the form, including the intention, and the priestly ordination of the celebrant. If these things are present, the Sacrament is valid, no matter what else is lacking. There are other defects, however, which may involve sin or scandal, even if they do not impair the validity of the Sacrament."

The holy Pontiff continues with regard for the form,

"If the priest were to shorten or change the form of the consecration of the Body and the Blood, so that in the change of wording the words did not mean the same thing, he would not be achieving a valid Sacrament. If, on the other hand, he were to add or take away anything which did not change the meaning, the Sacrament would be valid, but he would be committing a grave sin."

So, be careful about receiving questionable sacraments. Christ gave us the sacraments that we might gain Heaven, giving us the tools to be administered by His Church, by which we might acquire sanctifying grace and be strengthened in our resolve to defend and spread the Faith. Holy Communion, received validly, and often, nourishes the soul with good food, for it is written that "man cannot live by [earthly] bread alone." Scripture refers to the Eucharist as "supersubstantial bread" (not to be confused with any heretical consubstantiation et al.).
This all being said, do yourself the justice, and honour the Church by exercising an effort to learn the differences between the Mass of All Time (Tridentine) and the Novus Ordo. They do differ for a reason; otherwise there would be no reason to make changes upon what God established and gave to the apostles.

Domine Deo Nostro, miserere nobis.
Maria Mater Ecclesiae, ora pro nobis.
S. Therese, ora pro nobis.