How does the Cleric's Blessings of Knowledge feature interact with the rules for gaining proficiency when already proficient in a skill?

Question

Scenario:

I am a level 1 Half-Elf Monk, using a combination of my Monk starting skill proficiencies and Skill Versatility racial features to start with proficiency in Arcana, History, Religion, and Nature.

Upon hitting character level 2, I decide that with where I am in the plot at the time, it would make sense to multiclass into Cleric (and I have the proper prerequisites to do so)- this multiclass is not a preplanned decision made at character creation time.

I pick the Knowledge domain, which lets me pick two skills from Arcana, History, Nature, or Religion to become proficient in as part of the Blessings of Knowledge feature. My proficiency bonus is doubled for any ability check I make that uses either of the chosen skills I became proficient in.

By RAW, what skills can I ultimately gain proficiency in, and what skills get the doubled proficiency benefit of Blessings of Knowledge?

The rules for gaining proficiency in the same skill or tool from more than one source are as follows, according to PHB p.125:

If a character would gain the same proficiency from two different sources, he or she can choose a different proficiency of the same kind (skill or tool) instead.

I can see a few different ways to rule this depending on one's interpretation:

1. The above citation only applies to gaining proficiencies from backgrounds as it's in the "Backgrounds" section, despite the general language of "two different sources". As a result, I gain no proficiencies. I can still choose two of the listed skills to gain doubled proficiency bonuses.
2. The above citation applies. As a result, I still have to choose two out of Arcana, History, Nature, or Religion, but when that choice goes to give me proficiency in a skill I already have, I can then choose any other skill to gain proficiency in. Then, either:
   • The chosen skills out of Arcana, History, Nature, or Religion get the doubled proficiency bonus. The 'final' skills I newly gain proficiency in do not.
   • Only the 'final' skills I newly gain proficiency in get the doubled proficiency bonus.

Are any of the above interpretations correct?

Answer 1

I haven't been able to find any authoritative ruling on this anywhere, and the various People on the Internet who were talking about it had multiple different rulings, so I'd expect table variation.

At my table, I would rule that you can take a different skill (via the "if something gives you proficiency in a skill you already have you can pick another" rule that you quoted), but that the expertise would only apply to one of those four skills listed under Blessings of Knowledge (and you'd get it for the skill that you already had), so this isn't some backdoor way to get expertise in some random skill. That feels closest to the Rules as Intended IMO.

Answer 2

The quoted rule is intended to apply only to backgrounds

Rules designer Jeremy Crawford unofficially addressed a related question in a May 2018 tweet responding to a question about the Scout rogue's 3rd-level Survivalist feature (which grants double-proficiency in the Nature and Survival skills):

In PHB, it specifies that if you gain the same proficiency from two different sources, you may choose a different prof of the same type (skill or tool) instead. Does the survivalist rule for the Scout Rogue in XGE contradict this by stating"-if you don't already have it"?

The proficiency rule for backgrounds applies when you gain your background at 1st level. It has no relevance outside that context.

Per this ruling, any skill proficiencies gained beyond choosing your background at 1st level may not be substituted, unless the feature description specifically allows you to replace the redundant proficiency with a different one.

This matches the placement of the rule you quoted and the sentences immediately preceding it. Your quoted text appears in the "Proficiencies" subsection below the "Backgrounds" header, and says, in full:

Each background gives a character proficiency in two skills. [...]

In addition, most backgrounds give a character proficiency with one or more tools. [...]

If a character would gain the same proficiency from two different sources, he or she can choose a different proficiency of the same kind (skill or tool) instead.

As can be seen from the context, the rule allowing a character to replace one proficiency that would be redundant with another of the same type is specifically a rule that applies to proficiencies granted by backgrounds. It's not a general rule that applies whenever a skill or tool proficiency might be redundant; if it were, it would probably appear in a more general rules section.

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In this specific context:

If you were starting in the class at character level 1, since Knowledge clerics gain that subclass feature at level 1, you could simply plan ahead when choosing the background so that you're able to choose your preferred skills for the expertise (or rather, double proficiency) granted by Blessings of Knowledge.

However, if you don't plan ahead, you can not substitute the skills you get proficiency/double proficiency in past level 1.

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DMs may (and often will) house-rule otherwise

That said, this is simply an interpretation of the written rules. The DM can always house-rule otherwise, unless you're playing in the Adventurers League organized play system (which does not allow such house-rules).

In such a situation, if you're already proficient in a skill/tool and then a class feature tells you that you gain proficiency in that skill/tool (and possibly that you double your proficiency bonus), I suspect most DMs would allow you to reallocate your proficiencies so that the benefit of the feature is not wasted (as Garrett Rooney says he'd allow in his answer).

Especially when the feature is not gained at 1st character level, it can be strange/immersion-breaking for the character to be subpar/average at something, and then suddenly be amazing at it. For instance, this has sometimes occurred to me when playing a rogue that I planned on taking the Scout subclass with; I'd intentionally chosen not to be proficient in Nature or Survival at 1st level, because the subclass grants both proficiency and a doubled proficiency bonus ("expertise") in those two skills at 3rd level when the subclass is chosen.

That said, you shouldn't simply assume that every DM will allow this; if you're thinking of doing something like this, make sure to ask your DM first.