Here in the printer’s manuscript, Oliver Cowdery initially wrote “a clear conscience”, which is what we expect. He virtually immediately overwrote the final r of clear with an n (there is no change in the level of ink flow), thus ending up with “a clean conscience”, which is also possible (but not what we expect). Although the original manuscript is not extant for the book of Mosiah, Oliver may have intended to write clear in 𝓞, but as is typical of his hand, his r may have looked like an n. In the same way, even was sometimes mixed up with ever in the manuscripts, as in the two following examples where Oliver initially miswrote ever as even in 𝓟:
Similarly, one could argue, when Oliver came to copy Mosiah 2:15 from 𝓞 into 𝓟, he initially wrote the expected clear; but then, looking more closely at 𝓞, he determined that he had actually written the word there as clean (even though clear had been his original intention, no longer remembered). The 1830 compositor rejected the corrected reading in 𝓟 (clean) and set clear. All the subsequent printed editions have retained the expected reading, “a clear conscience”.
There is some evidence in the printer’s manuscript to support “a clear conscience” over “a clean conscience”. There is only one example, yet it is found in this same chapter (and as part of king Benjamin’s discourse to his people):
Here king Benjamin refers to having already said that he had served them “walking with a clear conscience before God”, a specific reference to the language previously expressed in verses 15 and 16. Such a connection argues that the use of clear is indeed the correct reading in verse 15—or at least that both should read the same, either as clear or as clean. David Calabro points out (personal communication) that one could argue that the clear in verse 27 is actually an error for clean—in other words, both verses 15 and 27 originally read “a clean conscience” and that Oliver wrote the first one down in 𝓞 as clean (correctly) but the second one as clear (incorrectly). When he came to copying from 𝓞 into 𝓟, his tendency to write clear showed up both times (but he corrected only the first one).
The tendency for Oliver Cowdery to write clear over clean may be due to the fact that “a clear conscience” was the expected expression of his time. The online Oxford English Dictionary lists eight occurrences of “a clear conscience”, with the following six citations within the same general time period of the Book of Mormon translation:
On the other hand, the online OED also lists one occurrence of “a clean conscience”, a citation from Early Modern English under the noun uphold:
One could argue that Oliver accidentally replaced the original two instances of “a clean conscience” (perhaps more appropriate for the biblical style of the Book of Mormon) with the expression “a clear conscience”, the phraseology that he himself expected.
From a semantic perspective, either reading will work. In support of clear, we first note that elsewhere in the Book of Mormon text the word conscience is found in only three places: Mosiah 4:3 (“peace of conscience”), Alma 29:5 (“joy or remorse of conscience”), and Alma 42:18 (“remorse of conscience”). All these other instances of conscience refer to one’s state of mind and are therefore either consistent with or in direct contrast to “a clear conscience”. One’s mind can be clean as well as clear, but with a difference in meaning. One could therefore argue that the phrase “a clean conscience” is unexpected here in Mosiah 2 since king Benjamin is not discussing his own personal sins, but the sins of his people and his own responsibility towards them. He has done everything he can for his people, and he is therefore blameless for their sins:
On the other hand, one could argue that king Benjamin’s language in Mosiah 2:27–28 actually implies that by his preaching he had made himself clean of the people’s guilt (“that your blood should not come upon me” and “that I might rid my garments of your blood”). Earlier, Jacob expressed the same idea—and more than once—when he referred to his need to be clean of the people’s guilt by ridding his garments and his soul of their iniquities and blood:
In these passages, Jacob does not explicitly use the word clean but it is clearly implied by his use of words like brightness and spotless. These passages provide some support for the argument that king Benjamin could refer to his conscience as being clean.
It is thus very difficult to decide the original reading for Mosiah 2:15 and Mosiah 2:27. We can be confident that both passages read identically, either as “a clear conscience” or as “a clean conscience”. Manuscript evidence, historical evidence, and internal evidence can all be used to support either clear or clean. Probably the safest decision is to follow the consistent reading of the printed editions; Oliver Cowdery’s manuscript readings, on the other hand, are inconsistent. But it should be understood that “a clean conscience” works about as well as “a clear conscience”, and that the original text may have actually read “a clean conscience” in Mosiah 2:15 and Mosiah 2:27.
One further question arises in Mosiah 2:15—namely, the use of the verb answer without any preposition before “a clear conscience”. In modern English, we expect the phraseology “I can answer with a clear conscience before God”. One wonders here whether with wasn’t lost in the early transmission of the text. Nonetheless, there are examples in the text where the verb answer seems to be missing an expected preposition:
For these two instances, modern English speakers expect the preposition for (“answering for the sins of the people” and “sins and iniquities / they shall be answered for”). Yet usage without the preposition for is found in Early Modern English, as in the following example from Christopher Marlowe (1590): “We were best look that your devil can answer the stealing of this same cup.” Such usage without the preposition for is now archaic in English; in fact, the OED uses the prepositional verb answer for to define the now-archaic meaning for such transitive uses of the verb answer: ‘to make a defense against a charge, hence to give a satisfactory answer for, to justify’ (see definition 4 under the verb answer). Of course, in Mosiah 2:15, king Benjamin says that he is answering a clear conscience, which is quite different from answering for sins and iniquities (as in Jacob 1:19 and Mosiah 29:30). Clearly, the meaning in Mosiah 2:15 is that the king is answering with a clear conscience, even if the preposition with is not expressed. But since the transitive verb answer can occur without an expected preposition (although in a different sense), the critical text will maintain in Mosiah 2:15 the reading without the preposition: “I can answer a clear conscience before God”. The reading is fairly transparent, has never been emended in any edition to read “with a clear conscience”, and could be intended.
Summary: Maintain the phrase “a clear conscience” in Mosiah 2:15 and Mosiah 2:27, the consistent reading in all the printed editions; the evidence suggests, however, that both “a clear conscience” and “a clean conscience” are equally probable readings for the original text; also maintain in Mosiah 2:15 the use of the verb answer without the preposition with since such usage could be intentional.