Does Comprehend Languages work through a Familiar?

Question

The comprehend languages spell says:

For the duration, you understand the literal meaning of any spoken language that you hear. You also understand any written language that you see, but you must be touching the surface on which the words are written. It takes about 1 minute to read one page of text.

A wizard who casts find familiar can see through the familiar's eyes and gets the "senses" of the familiar as well. Does that mean touching a written language through a Familiar counts as "you" (i.e. the wizard) touching the surface?

Answer 1

You are asking two questions; however, I will address both.

First, the functioning of find familiar's sense-sharing action must be addressed.

[A]s an action, you can see through your familiar's eyes and hear what it hears until the start of your next turn, gaining the benefits of any special senses that the familiar has. During this time, you are deaf and blind with regard to your own senses.

These "special senses" include senses such as darkvision and tremorsense (Basic Rules for Dungeon Masters, section Monsters -> Statistics -> Senses). This does not mean the caster feels what the Familiar feels, nor does the caster touch what the Familiar touches.

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Does touching a written language through a Familiar count as the caster touching the surface?

No. As stated above, nowhere in find familiar does the spell say that the caster counts as touching the objects touched by the Familiar when sharing its senses.

Additionally, since comprehend languages is a spell of range "self" rather than "touch," the Familiar cannot cast comprehend languages for the caster to circumvent this. A Familiar can only deliver its caster's touch spells.

[W]hen you cast a spell with a range of touch, your familiar can deliver the spell as if it had cast the spell.

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Does comprehend languages work through a Familiar?

There are two situations where this would work through a Familiar. Remember that sight and sound, as well as special senses, are shared with the caster.

1. Comprehending written text: As long as the caster is touching the text's surface and can see through their own eyes or through their Familiar's, the spell would work. As stated above, though, the caster must be touching the surface. It is not sufficient that the Familiar touch it.
2. Comprehending spoken language: The caster need only hear the spoken text to comprehend it. If the caster hears spoken text through the Familiar, then this would work.

Important note: The caster must spend an action every round in order to maintain the reception of the Familiar's senses. If the caster cannot take an action or is otherwise forced to use a different action, then the caster cannot comprehend languages through the Familiar until the caster again takes this action. The duration of comprehend languages is one hour, so this should normally not be a problem in a safe area.

Answer 2

No, the effects of Comprehend Languages and using your familiar's senses are mutually exclusive

Because the description of comprehend languages uses the word "you", it would appear that this does not extend to your familiar, as further supported by the fact that the find familiar spells says (PHB, pg. 240):

... you can see through your familiars eyes and hear what it hears until the start of your next turn, gaining the benefits of any special senses it has. During thus time, you are deaf and blind with regards to your own senses.

However, later in the description of Find Familiar, it says this (PHB, pg. 240):

Finally, when you cast a spell with a range of touch, your familiar can deliver the spell as if it had cast the spell.

Since comprehend languages has a range of "self, not "touch", the familiar cannot cast the spell, and thus the senses affected are yours, not the familiar's.

Since you are "gaining the benefits of any special senses it has" and are "deaf and blind with regards to your own senses", this would mean that since you are the one affected by the comprehend languages spell, and you cannot see or hear anymore, then anything the familiar sees or hears "for you" doesn't count as you hearing it, since your are deaf, or seeing it, since you are blind.

Therefore, you cannot understand languages through your familiar as you intend.