According to Calvinism, if Catholicism might lead to salvation, why to remain a Calvinist? (Henry IV story)

This is a typical problem in Bayesian Probability Theory.

If salvation is possible for Catholics, given Calvinism is true, and impossible for Calvinists, given Catholicism is true; then IF Calvinism and Catholicism are equally likely ( in Henry's opinion) he maximises his chances by choosing Catholicism.

But if he thinks Calvinism is more likely to be true, then the optimal relgion depends on exactly how possible, orlikely, it is Catholics will be saved if Calvinism is true.

Suppose he decides he is 70% sure Calvinism is true, and Catholics have a 40% chance of salvation if it is. Then his chance of salvation if he chooses Catholicism is

((probability Catholicism is true) x (prob of salvation if it is)) + ((probability Calvanism is true) × (prob of salvation if it is) = 30% x 100% + 70% × 40% = 58 %.

But if he chooses Calvinism his chance of salvation is 70%, so this is the safest choice.

This area of probability was investigated by Reverend Thomas Bayes who was an eighteenth century Calvinist minister. As far as I know, he never applied his theory to choosing his religion.

Added in response to luchonacho comment:

My maths assumes, based I think on your question, that there are 4 possible scenarios.

A) Catholicism is true, and Henry becomes Catholic (he guesses right!).

B) Catholicism is true, but Henry remains Calvinist (he guesses wrong)

C) Calvinism is true, and Henry remains Calvinist (he guesses right)

D) Calvinism is true, but Henry becomes Catholic (he guesses wrong).

If he guesses right he will be saved. This means that in scenarios A and C the probability of salvation is 100%. In scenario B Henry will be damned because there is no salvation outside the RCC, the probability of salvation is 0%. In scenario D he might be saved, according to the belief that if Calvinism is true, Catholics might be saved.

For scenario D Henry must decide how likely it is that, in fact, a Catholic will be saved if Calvinism is true. He must also decide how likely he thinks it is that Catholicism is true.

Let S be the probability that a Catholic is saved assuming Calvinism is true, and let P be the probability that Catholicism is in fact true.

If Henry believes that Catholicism and Calvinism are equally likely to be true then, however small S is, he should plump for Catholicism as giving him the best chance. Also if he thinks Catholicism more likely than Calvinism to be true he should, of course, pick the RCC.

The difficulty is what to do if he thinks Calvinism is most likely to be true. If there is very high chance Calvinism is true, and only a small chance a Catholic will be saved if it is, then he should bet orange by choosing Calvinism.

Of our four scenarios his hopes of salvation are

A) P

B) 0

c) 1 - P

D) (1 - P) x S

If he chooses Catholicism (bets green) his salvation chance is P + ((1-P) xS) but if he chooses Calvinism (bets orange) it is 0 + 1 - P.

If 1 - P > P + ((1-P) xS) then he should pick Calvinism.

The point of indifference is where S = (1-2P)/(1-P) and P = (1-S)/(2-S).

So the more likely he thinks it is that Calvinism is true, the more likely he must believe Catholics wil be saved if it is, in order for Catholicism to be the best bet.

I completely agree a more theological answer would be better, and look forward to reading one. I hope the math is now a little clearer though.

The Calvinist answer to the question "is there salvation in the Catholic Church" is "yes and no." It is "no" because there is nothing salvific in being affiliated with the papacy. We deny the legitimacy of the office of pope, in addition to many other unbiblical offices and deny sacerdotalism entirely as a scheme of salvation. A person whose hope for a basis of salvation is placed in the pronouncements or presumed dispensation of grace at the discretion of Roman Catholic priests is someone a Calvinist would consider unsaved or at least very confused and saved in spite of it.

The "yes" part of the question is based on the belief that salvation is found in Jesus alone and it is fully possible to be a member of a corrupt church and yet be a sincere believer.

The idea that a person would be a Catholic "just to be safe" would imply that they are not trusting in Christ for forgiveness but rather in their church membership or placing their hope in men. The Calvinist position is that salvation is by direct faith in Jesus Christ alone, not faith plus works, nor faith plus membership/blessing by a priest. We don't recognize apostolic succession as a legitimate biblical concept except in the succession of apostolic doctrine.

Reformed confessional documents rarely even offer the name "Roman Catholic" as a courtesy, preferring names like "papcy" and "papist" due to a lack of desire to grant the premise that "Catholicism" is "catholic" (i. e. the universal church). The Westminster Confession of Faith in the chapter on marriage forbids marriage with "papists and other idolators" (chapter 24).

The default posture of Calvinism towards Rome is to view them as a mission field in the form of a true church that has been corrupt (hence we recognize Roman baptisms as legitimate baptisms whereas the baptisms of heretical churches like LDS or Jahovah's Witnesses we would not recognize and would judge that the person would need to be baptized for the first time).