Might Edward Feser be using "Circular Logic" in saying "there can be no reasonable doubt that Benedict Validly Resigned"?
It is also a non-starter even apart from all that, because there can be no reasonable doubt that Benedict validly resigned. Canon 332 §2 of the Code of Canon Law tells us:
If it happens that the Roman Pontiff resigns his office, it is required for validity that the resignation is made freely and properly manifested but not that it is accepted by anyone.
Now, Benedict publicly and freely resigned his office, and has publicly reaffirmed that his decision was taken freely, in answer to those who have speculated otherwise. He has also explicitly acknowledged that there is only one pope and that it is Francis. His resignation thus clearly meets the criteria for validity set out by canon law. End of story.
Some have
suggested that the resignation cannot have been made freely because, they say,
it was done under the influence of an erroneous theory of the papacy, namely
the one described by Gänswein. But this
is a non sequitur, as any Catholic
should know who is familiar with the conditions for a sin to be mortal – grave
matter, full knowledge, and deliberate consent. My point isn’t that Benedict’s resignation
was sinful, but rather that these conditions illustrate the general point that
the Church distinguishes acting with full
knowledge and acting with deliberate
consent or freely. And canon law
makes only the latter, and not the former, a condition for the validity of a
papal resignation. Hence, even if
Benedict’s resignation was made under the influence of an erroneous theological
theory about the papacy, that would be irrelevant to its having been made
freely and thus validly. - Dr. Edward Feser [http://edwardfeser.blogspot.com/2022/04/benevacantism-is-scandalous-and.html]


He resigned because God accepted his resignation. How do we know God accepted His resignation? Because he resigned.
You have not answered the Canonical question - which is very, very simple - it required one sentence and equivalent action: “I resign the Munus. I am no longer Pope but Father Ratzinger. Good bye”.
But that didn’t happen, did it?
The Catholic Monitor commenter Aqua and an Edward Feser-like "Francis is infallibly definitely the pope" guy named Michael O'Hearn fought a couple of rounds in the CM comment section with O'Hearn apparently using logic similar to Feser as quoted above. You decide who won the fight:

Dr. Mazza’s explanation of Benedict’s conception of the papal office as forever gift conferred by God is accurate. This also explains why Benedict did not refer to munus in his declaratio of February 2013.
Benedict’s explanation a la nouveau theologie seems to be that the later distinction incorporating a separate concept of potestas iurisdictionis was in fact a medieval accretion imposed by the exigencies inherent in the feudal system set up in Europe after the fall of the Roman Empire, and not without a secular purpose.
One can look at the papal prerogatives in either sense without necessitating the nullification of the resignation.

On Nov 18, 2021, Michael O'Hearn said: Father Kramer asserts [The Case Against Bergoglio, digital version page 479]: ““The incontestable fact that Pope Benedict XVI has maintained some claim on his papal munus proves absolutely, that he remains in full possession of the primacy as a result of the conditionality of his renunciation of the munus.
Michael O'Hearn commented on "Flashback: "Saruman" Taylor Marshall's False Dichotomies on Francis"
Nov 18, 2021
Father Kramer asserts [The Case Against Bergoglio, digital version page 479]: ““The incontestable fact that Pope Benedict XVI has maintained some claim on his papal munus proves absolutely, that he remains in full possession of the primacy as a result of the conditionality of his renunciation of the munus. The reason for this is that the nature of the papacy is such, that the actual holder of the office possesses the primacy in virtue of the Petrine munus which he possesses in its absolute and indivisible fullness, so that a pope who would attempt to renounce the papal office by an act that lacks a total and unconditional renunciation of the munus, by the very act of his stipulating a qualifying condition of the renunciation, whereby the intention is asserted in the act, to retain anything whatsoever of the munus he received from Christ upon his election, albeit only “spiritual” and not jurisdictional, nullifies the act in virtue of the fatal equivocation brought about by the logical opposition of contradictory assertions made in the act.” Excerpt From On the true and false pope Paul Kramer https://books.apple.com/us/book/on-the-true-and-false-pope/id1595649148 This material may be protected by copyright.

I contend that God does accept Benedict’s resignation and so reject the sedevacantist conclusions reached by some.

You didn’t make an argument. You made a declaration. What is the argument?

Canon 332.2: “Canon 332 §2 of the Code of Canon Law provides that: “[i]f it happens that the Roman Pontiff resigns his office, it is required for validity that the resignation is made freely and properly manifested but not that it is accepted by anyone.”


He resigned because God accepted his resignation. How do we know God accepted His resignation? Because he resigned.
You have not answered the Canonical question - which is very, very simple - it required one sentence and equivalent action: “I resign the Munus. I am no longer Pope but Father Ratzinger. Good bye”.
But that didn’t happen, did it?

https://file.wikileaks.org/file/?fbclid=IwAR2U_Evqah_Qy2wxNY12FMqFC5dAFUcZL5Kl4FIfQuMFMp8ssbM46oHXWMI
This is the post they were fighting about:
Catholic historian Edmund Mazza explains why Pope Benedict XVI's resignation appears to be in "substantial error" and is therefore not a valid "papal resignation":
De Mattei writes:
This doctrine [the distinction between Power of Order and Power of Jurisdiction]…has also been the common practice of the Church for twenty centuries, can be considered one of divine law, and as such unchangeable.[xxvi] Vatican Council II did not explicitly reject the concept of “potestas,” but set it aside, replacing it with an equivocal new concept, that of “munus.” Art. 21 of “Lumen Gentium” then seems to teach that episcopal consecration confers not only the fullness of orders, but also the office of teaching and governing, whereas in the whole history of the Church the act of episcopal consecration has been distinguished from that of appointment, or of the conferral of the canonical mission. This ambiguity is consistent with the ecclesiology of the theologians of the Council and post-council (Congar, Ratzinger, de Lubac, Balthasar, Rahner, Schillebeeckx…) who presumed to reduce the mission of the Church to a sacramental function, scaling down its juridical aspects…
Ratzinger…distanced himself from tradition when he saw in the primacy of Peter the fullness of the apostolic ministry, linking the ministerial character to the sacramental (J.Auer-J. Ratzinger, La Chiesa universale sacramento di salvezza, Cittadella, Assisi, 1988).[xxvii]
Benedict would counter that Vatican II taught that “collegiality is not based on a papally conferred jurisdiction, paralleling the sacrament of ordination as though that sacrament were merely an individual gift; rather, collegiality reaches into the very essence of the sacrament, which as such carries within it an intrinsic correlation to the community of bishops.”[xxviii] Or again, “the sacramental-ontological munus…ought to be distinguished from the canonical-juridical aspect.” This is why Benedict went to great pains NOT TO RENOUNCE THE PETRINE MUNUS AS SUCH in his 2013 “Declaratio.”[xxix]
But Vatican II was referring to the episcopacy, not the papacy.
The ultimate question then is whether what was subjectively in Benedict’s mind was an accurate or erroneous understanding of the objective reality of the munus Petrinum in the Church’s ecclesiology. If one’s will acts on an erroneous appraisal presented to it by one’s reason, the WILL DOES NOT CHOOSE FREELY. Mistakes of this kind are most frequent in attempts at marriage. Marriage is an objective state of being that does not come into existence except from a free act of the will, which is dependent upon accurate knowledge:
error invalidates the act if it is an error concerning the substance of the act…Error affects consent, for the will in an act of consent elects an object presented to it by the mind. If the mind is in error, the object is imperfectly or incorrectly presented and choice made upon such a premise is not always the same choice that would have been made if the object were correctly known.[xxx]
And we might add in closing, that according to the Church’s law, a resignation must also be “properly manifested” in order to be valid. But since objectively Benedict renounced “the ministry” of Bishop of Rome, and not the “munus,” there is ambiguity—not clear manifestation. In fact, even if ministry meant the same thing as munus in canon law (which it does not), or even if Benedict had explicitly mentioned “the munus” of Bishop of Rome, we could not be sure whether he meant munus as office [potestas iurisdictionis] in accord with canon law and centuries of tradition or if he meant munus as rite [potestas ordinis], which he has argued for decades is irrevocable:
The ministry [munus] of the bishop is not an externally assigned “administrative power,” but rather arises from the necessary plurality of the eucharistic communities (i.e., of the Churches in the Church) and, as representing these, is itself sacramentally based. The ruling of the Church and its spiritual mystery are inseparable. Only by dealing with this issue in such depth does the text [LG 22] make possible a “decentralization” of the Church that will progress beyond a merely opportunistic organizational change and move into the sphere of genuine spiritual renewal. [https://www.edmundmazza.com/2021/04/21/leave-the-throne-take-the-ministry-the-sacred-powers-of-pope-emeritus/]
So to speak, it appears that Mazza is saying that Benedict needs an annulment from his erroneous "attempt at" resignation. Here are some impediments to a valid marriage:
Impediments
If one of the parties were prohibited from marrying by a diriment impediment (from the Latin for "interrupting"), the marriage is invalid. Because these impediments may not be known at all, the marriage is called a putative marriage if at least one of the parties married in good faith.
Diriment impediments include:
- One or both parties is below the absolute minimum age of 16 for males and 14 for females[10]
- Antecedent and perpetual impotence (not to be confused with sterility)[11]
- Ligamen, or being already married[12]
- The situation in which one party is a Catholic and the other has not been baptized (unless a dispensation is granted)[13]
- The man was ordained to holy orders[14]
- Either party made a public perpetual vow of chastity in a religious institute[15]
- Abduction with the intent of marriage (known as raptus), is an impediment as long as the person remains in the kidnapper's power[16]
- Impediment of Crime, bringing about the death of one's spouse, or the spouse of another, with the intention of marriage[17]
- Consanguinity, or close relationship by blood, even if the relationship is only by law[18]
- Affinity, or close relationship by marriage. [https://en.wikipedia.org/wiki/Declaration_of_nullity]
Here are some grounds for nullity:
Grounds for nullity
A marriage may be declared invalid because at least one of the two parties was not free to consent to the marriage or did not fully commit to the marriage.
Grounds for nullity include:
- Simulation of consent; that is, the conscious and positive exclusion at consent by either or both of the contracting parties of one or all of the essential properties or "goods" of marriage: a) exclusivity of the marital relationship; b) the permanence of the marital bond; c) openness to offspring as the natural fruit of marriage (canon 1101§2)
- Deliberate deceit about some personal quality that can objectively and gravely perturb conjugal life (canon 1098)
- Conditional consent, if the condition at the time of marriage concerns the future, or if it concerns the past or present and is actually unfulfilled (canon 1102[20])
- Force or grave fear imposed on a person to obtain their consent (canon 1103)
- A serious lack of the discretion of judgment at consent concerning the essential matrimonial rights and duties mutually to be handed over and accepted (canon 1095 n.2)
- Psychic incapacity at consent to undertake the essential obligations of marriage (canon 1095 n.3). [https://en.wikipedia.org/wiki/Declaration_of_nullity]
Canon 332.2: “Canon 332 §2 of the Code of Canon Law provides that: “[i]f it happens that the Roman Pontiff resigns his office, it is required for validity that the resignation is made freely and properly manifested but not that it is accepted by anyone.”