This is completely unsurprising

…and yet also instructive.

A Protestant insists:

You know very well that the doctrine of perspicuity relates only to those things which are necessary to be known for salvation.

A Catholic responds:

Who decides the list of “those things”?

What is YOUR list?

Just so. Because, of course, if these things are perspicuous in Scripture, it should be pretty easy – especially after 500 years of Protestant contemplation – to let us all know what those things are.

Predictably, however, it is at this point that the evasions begin. Our Protestant replies:

"Who decides the list of “those things”?"

God

"What is YOUR list?"

See previous answer.

To be sure, this is a precise answer; to be equally sure, it is evasive precisely because its author is one who is surely bright enough to comprehend what his Catholic interlocutor is asking: that is, we would like to know what God's list of these perspicuous things consists of.

The Catholic pursues:

And what is God’s list?

Understand: the question has nothing to do with obscure theological minutiae. No. Nor does it have to do with jargon or concepts foreign to the Protestant's own milieu. No. It is the Protestant who has made the claim to perspicuity relating to certain things here. Is it unreasonable, then, to suppose that an enumeration exists of "those things which are necessary to be known for salvation"?

The Protestant replies:

You mean you want me to discern the contents of the list and provide them for you? I'd be hesitant to try to do that for you.

Astonishing. Why would he have to "discern" the list? One would think that perspicuous things would have already been found (once again, considering that Protestants have had 500 years to think about it). It seems reasonable, then, that we could find that list in just about any Protestant book, and on every Protestant website. It seems reasonable that we could find it at the very least in the books and websites of our Protestant's co-religionists, and it seems entirely reasonable to suppose that we ought to be able to find such a list on the website or in other writings of the very man making the claim.

And yet we don't.

Or…rather…sometimes we do, but those lists never seem to agree, and that very fact pretty much puts the kibosh on the whole "perspicuous" thing. But I digress. How is it that our Protestant has to "discern" these things? Why on earth hasn't he already established what the list is? This is very shocking if his claim is true (that such things are readily known from the Bible).

And why on earth would he be hesitant to do that? First, why would he be hesitant to do it for a Catholic, whom he more than likely supposes is not a Christian? Why would he be hesitant to do it for anyone he considers a non-believer? Why hasn't he already done it for himself (I presume that he hasn't done so, given that he says he would have to "discern the contents of the list," which implies that he hasn't done so already)?

None of this is surprising. I would have had the same difficulties when I was Protestant if someone had pinned me down this way. The fact is that the theological, philosophical, and epistemological problems surrounding sola scriptura and the Protestant doctrine of the perspicuity of Scripture are insurmountable.