When critiquing the doctrine of sola scriptura, some Catholics take as their target the idea that all doctrines must come from the Bible. From this, it’s argued that the Bible doesn’t teach this, and therefore sola scriptura is self-refuting.
But Protestants are quick to respond that this line of argumentation misses the mark, since it runs on an inaccurate understanding of sola scriptura. “The real definition of sola scriptura,” so it’s said, “is that the Bible is the sole infallible rule of faith.”
Whether this response dodges the Catholic challenge or not is a question that I’ll put off to the side for now. What I want to focus on here is how a Protestant arrives at the doctrine.
In a recent debate with Trent Horn, Protestant apologist Gavin Ortlund gave the following argument in defense of sola scriptura:
P1: The Bible is an infallible rule for the Church.
P2: There is no other infallible rule for the Church.
C: Therefore, the Bible is the only infallible rule for the Church (which is the doctrine of sola scriptura).
Horn did a great job in tangoing with Ortlund’s argument, pointing out various weaknesses and failures. There is one problem, however, that was not mentioned and is worth highlighting here. (No fault on Horn’s part, as I’ve had the privilege of reflecting on Ortlund’s argument at my leisure as opposed to being in the hot seat.)
In defense of premise one above, Ortlund argued that the Bible is an infallible rule for the Church because of its “ontological nature.” “It’s inspired,” he said, “the speech of God through a human being. And it’s on that basis that we speak of Scripture as infallible.” So Ortlund’s argument so far is basically this:
P1.1: If an authority for the Church is inspired, then it is an infallible rule for the Church.
P1.2: The Bible is an authority for the Church that is inspired.
P1.C: Therefore, the Bible is an infallible rule for the Church.
So far, so good! But Ortlund’s next step is where his argument runs into trouble.
Ortlund claimed that “Scripture is ontologically unique in its nature.” “No other rule of faith,” he continued, “is the God-breathed, Spirit-carried, unbreakable oracle of God.” In other words, Ortlund is saying there’s no other authority for the Church that is “inspired.” We can re-formulate premise two of Ortlund’s main argument as follows:
P2.1: If an authority for the Church is not inspired, then it is not an infallible rule for the Church.
P2.2: No authority for the Church besides the Bible is inspired.
P2.C: Therefore, no authority besides the Bible is an infallible rule for the Church.
Taken by itself, the above argument is valid. But remember: it is only a piece of the puzzle. When we combine it with the justification for premise one of Ortlund’s main argument, it becomes clear that the argument is invalid.
In logic, a conditional premise is an “if . . . then” proposition. For example, “if it’s raining outside, then the ground is wet.” The antecedent is the “if” part of the proposition. The “then” part is called the consequent. Consider this line of reasoning, for example:
1) If it’s raining outside (antecedent), then the ground is wet (consequent).
2) It’s not raining outside (negation of antecedent);
3) therefore, the ground is not wet (negation of consequent).
This argument is an example of the fallacy of negating the antecedent, which makes for a logically invalid argument.
It’s fairly easy to see why the above conclusion doesn’t follow: rain and wetness are not logically identical to each other. We can deny rain and still have wetness because there are other ways besides rain in which the ground outside could be wet—e.g., the water hose could be lying on the ground running with water.
How does this logical fallacy apply to Ortlund’s argument? Ortlund argues that if an authority for the Church is inspired, then it is an infallible rule for the Church (P1.1). But then he says there is no authority for the Church besides the Bible that is inspired (P2.1). This is a negation of the antecedent.
Ortlund then makes a conclusion based on this negation—namely, no authority besides the Bible is an infallible rule for the Church, which is the definition of sola scriptura. Notice that this is a negation of the consequent in P1.1. And to conclude with a negation of the consequent based on the negation of the antecedent is to commit the fallacy of negating the antecedent, at least when the antecedent is not logically identical to the consequent.
Like rain and wetness, inspiration and infallibility are not logically identical. Inspiration entails that what is affirmed by the human authors is affirmed by God. Infallibility entails that the biblical authors, when writing, were incapable of teaching error.
The conceptual content is different. Such difference is easy to see when we consider that God can make someone incapable of error without inspiring him. God could providentially order events such that the person can’t teach the error—e.g., the author changes his mind on the issue and conform to the truth, circumstances don’t allow him to write the error down, God wills his death, etc.
To make it really simple, the ground can be wet without it having rained, and a Christian authority can be an infallible rule for the Church without being inspired. So even if it were true that the Bible is the only inspired authority for the Church, that would not rule out other non-inspired authorities—for example, the pope speaking ex cathedra on faith and morals—as infallible rules for the Church, too. Even on Ortlund’s own argumentation, he can’t get sola scriptura to where he wants it to be. To do that, he’d have to establish in his premises that there’s no other way besides being inspired that an authority in the Church can be infallible.
The sola scriptura doctrine, therefore—at least as it’s argued for by Ortlund—is a doctrine that is based on the fallacy of negating the antecedent. I suspect that many other Protestants argue along the same lines. And given the invalidity of this line of argumentation, we can’t accept its sola scriptura conclusion.