Rereading Fr. Laisney's excellent article, it makes brilliant points, and is worth citing here, especially this part:
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In other words, salvation, which is at the end of the Christian life on earth, only requires perseverance in the state of grace received at justification, which is at the beginning of the Christian life on earth. Baptism is the sacrament of justification, the sacrament of the beginning of the Christian life. If one has received sanctifying grace, which is the reality of the sacrament - res sacramenti - of baptism, he only needs to persevere in that grace to be saved. Perseverance in grace requires obedience to the Commandments of God, including the commandment to receive the sacrament of baptism. Thus there remains for him the obligation to receive baptism of water. But, this is no longer absolutely necessary (by necessity of means), since he has already received by grace the ultimate fruit of that means. It still remains necessary in virtue of our Lord’s precept to be baptized by water. When and if circuмstances independent of our will prevent us from fulfilling such a precept, the principle taught by St. Cyprian, St. Ambrose, St. Augustine, and others is to be applied: "God takes the will as the fact."[9] This means that God accepts the intention to receive the sacrament of baptism as equivalent to the actual reception of the sacrament.It is false to pretend that Canon 4 of Session VII (TCT 668) of the Council of Trent (quoted above) on the "Sacraments in General" deals with justification as opposed to salvation. Desire is explicitly mentioned in this canon, for when it uses the expression "aut eorum voto," it admits that the grace of justification can be obtained by desire of the sacraments. It is also false to say that Canon 5 on the Sacrament of Baptism from Session VII of the Council of Trent deals with salvation as opposed to justification. Indeed Canon 4 (of Session VII) deals explicitly with the necessity of sacraments "for salvation." In that context, the expression "grace of justification" appears manifestly as being precisely the only essential requisite for salvation, as is taught explicitly in Session VI, Chapter 16. That which is said of the sacraments in general applies to each sacrament in particular, without having to be repeated each time. Simplistic reasoning which disregards the explicit teaching of the Church on baptism of desire only arrives at false conclusions.
That it is not necessary to repeat the clause "re aut voto" is so much the more true since baptism of desire is an exception, a special case, not the normal one. One need not mention exceptions each time one speaks of a law. For instance, there are many definitions of the Church on original sin that do not mention the Immaculate Conception. This does not invalidate the Immaculate Conception! For instance Pope St. Zosimus wrote: "nullus omnino —absolutely nobody" (Dz 109a) was exempt of the guilt of original sin. Such a "definition" must be understood as the Church understands it, that is, in this particular case, not including the Blessed Virgin Mary. In the same way, it is sufficient that baptism of desire be explicitly taught by the Church, by the Council of Trent, in some place, but it is not necessary to expect it on every page of her teaching. Silence on an exception is not a negation of it. This principle is important to remember so as not to be deceived by a frequent technique of the Feeneyites. They accuмulate quotes on the general necessity of baptism as if these quotes were against baptism of desire. The very persons they quote hold explicitly the common teaching on baptism of desire! These quotes affirming the general necessity of baptism do not refer exclusively to baptism by water, nor do they exclude baptism of blood and/or of desire. They are to be understood "in the same sense and in the same words" as the Catholic Church has always understood them, which means to include baptism of blood and/or of desire along with that of water." ...