An Important Note in Sacramentology
Sacraments as Signs
It often happens that, when one error arises, another error replaces it at the opposite end of the spectrum. In the error, common among many sects of Protestantism, that a sacrament is a mere symbol, the opposite error arises, stripping the sacraments of symbolic consideration.
The Fathers and Theologians have always described the sacraments as a sign; it is, of course, unique in the genus of sign insofar as it causes the grace that it signifies, yet a sign nevertheless. A sign garners its precise notion from its order to an intellect. It is meant to cause knowledge of some reality. Therefore, if we are not attentive to the precise nature of a sacrament as a sign, then our sacramentology will be quite deficient.
“Yes, we know that it is a sign, yet we focus on the effect of the sacrament, so what is the harm?” In this common sentiment, there is a subtle error that is quite hard to catch. A sign is determined as such and such a sign by what it primarily signifies. The sacraments primarily signify the internal grace communicated by the sacraments. This much is true. Yet, the subtle error is to go from the premise that the sacraments primarily signify the grace given in the sacrament to the error that the sacraments exclusively signify the grace given in the sacrament.
Since the sacrament is a practical sign, there are two lines that we can distinguish in the sacrament. First, the line of formal causality, i.e., what the sacrament formally gives, the grace that it formally contains, e.g., in baptism the grace of regeneration. Second, the line of intentional causality, i.e., what the sacrament reveals to the intellect.
Let’s say that God chose to sanctify us all at once and perfect man in an instant rather than gradually leading us from grace to glory as he does now; under this supposition, the line of formal causality and the line of intentional causality would be one and the same. There would be no distinction between these two orders. Yet, God has not chosen to sanctify us in this way, choosing to, in accordance with our human condition, gradually bring us step-by-step from grace to glory, through various different stages of the spiritual life. Hence, the graces given in the sacraments signify much more than they formally give. The intentional line, therefore, is much broader than the formal line.
In the formal line are signified sanctifying grace and those particular, unique graces given in each of the sacraments. In the intentional line is signified the total effect of sanctifying grace in general and of those unique graces in particular. Since all are called to mystical perfection, each and every sacrament signifies within itself the total development of the supernatural organism and its highest development (including the unitive way, the perfection of the spiritual life on earth, to which we are all called), along with the glory of heaven. Further, each particular sacrament signifies within itself the perfect development of those particular graces that are given in the sacrament (especially applicable to matrimony and holy orders).
Yet, there is even greater news. There is actually a vital union between these two lines outside of merely the intentional (intellectual) order. Not only do these sacraments signify these perfect realities, but they also cause these perfect realities.
Note that I said that these sacraments signify much more than they formally give. While they only formally give the beginnings and inchoate form of these higher realities, these sacraments virtually give the full development of these higher realities. When one plants a seed into the ground, only a seed is formally given, yet the entire tree in all its vitality is virtually given to the ground.
God, who is faithful and just, always more willing to give than we are to ask, has given and promised the perfection and full development of these graces to those who worthily make use of the ordinary means, including mortification, prayer, and the sacraments. The faithful soul can be assured that God, who infallibly grants these beginnings to those who do not place an obstacle in the way, will also infallibly grant the perfection of these graces to those who make good use of those same sacraments. Thus, the full line of intentional causality is either virtual (for all) or formal (for those who are perfect), yet is absent from none.

Beautifully and succinctly said. Is there a work you would recommend that explains both the formal and intentional “lines” of each sacrament? I would be especially curious to see the full “intentional lines” behind the Eucharist and Penance.