In the printer’s manuscript scribe 2 initially wrote “did exceed the whiteness”; then he crossed out the definite article the and supralinearly inserted all. The level of ink flow for the correction is somewhat heavier; but his crossout and his insert mark are of the same level of ink flow, so scribe 2 may have simply dipped his quill just before writing the supralinear all. Scribe 2 of 𝓟 does not appear to be an “editing” scribe; that is, his only purpose was to faithfully copy the text. There is virtually no evidence of him ever trying to correct “mistakes” in the text. Therefore, his correction to “all whiteness” was probably the reading of the original manuscript. On the other hand, the 1830 compositor himself set “all the whiteness”, which doesn’t sound quite right (but which has been maintained in all the printed editions, including the RLDS ones).
The question is why would scribe 2 of 𝓟 initially write “the whiteness” and the 1830 compositor set “all the whiteness” if there was no the in 𝓞? One possibility is that each was influenced by the two other occurrences of whiteness in this passage, both of which are preceded by the:
The closeness of the first occurrence of “the whiteness” could have easily led both scribe 2 of 𝓟 and the 1830 compositor to accidentally add the the (but with only scribe 2 catching his error). Perhaps even more significant is the fact that the last occurrence of “the whiteness” would have been right below the instance of “all whiteness” in 𝓞, as it is in 𝓟:
Since here both 𝓟 and the 1830 edition are firsthand copies of 𝓞, contamination from the two nearby occurrences of “the whiteness” could have led to “the whiteness” initially in 𝓟 and to “all the whiteness” in the 1830 edition.
The phrase “all the whiteness” (the 1830 reading) is indeed odd unless there is some postmodification of whiteness, as in the following example:
In that case, whiteness is modified by a relative clause. Similarly, there are two instances later on in 1 Nephi where “the whiteness” occurs, and there the phrase is again postmodified (either by thereof or by a prepositional phrase):
Otherwise, when all is found along with the verb exceed, we do not expect the the unless the following noun is postmodified; the following example shows the contrast:
For 3 Nephi 19:25, the best solution would be to accept the corrected reading of 𝓟 (“all whiteness”) as the original reading, which was probably the reading of 𝓞.
Summary: Restore in 3 Nephi 19:25 the corrected reading in 𝓟: “behold the whiteness thereof did exceed all whiteness”; the occurrence of “all the whiteness” in the 1830 edition seems to have been an error based on the two occurrences of “the whiteness” in this passage; in a similar manner, scribe 2 of 𝓟 initially wrote “the whiteness” instead of the correct “all whiteness” in this sentence.