Jacob's excursion into Zenos' allegory is specifically to answer a question he has posited: "Jacob 4:17 And now, my beloved, how is it possible that these, after having rejected the sure foundation, can ever build upon it, that it may become the head of their corner?"
This allegory will be a description of the Lord's efforts with the children of Israel, and as a grand explanation of the efforts of the great husbandman, it will show how the ultimate reconciliation of the Jews will occur so that they may build upon the firm foundation of the Son of God.
In the context of this discourse, the allegory serves to deal with a question arising from the preaching of the coming Christ. Nephi and Jacob have preached of Christ, and preached of a crucified Christ. The Messianic expectation set by Isaiah would be of a triumphant Messiah (though the prophecies also refer to the mortal ministry of the savior, the major themes are eschatological). Jacob is here addressing what must have been a puzzling aspect of the prophecies of Christ. How might one reconcile a rejected and crucified Messiah with the triumphal Messiah? How can one who is rejected by Israel become the leader of Israel? Jacob presents the answer through scripture. His explanation is not from his own words, but based in scripture. It will also be typical of the way he and Nephi cite scripture, largely uncommented, and presented as self-evident.
Literary: Analogies such as Jacob quotes from Zenos are not uncommon in the scriptures. The metaphorical/allegorical use of agricultural practices is only to be expected for a people whose lives where much more intimately bound to the earth than are those of modern man. However, the use of such analogies from life to teach a truth go further than simply using the example from nature to teach a point. The significant use of these depends not solely upon the understanding of the processes of nature, but upon readily established symbolic associations.
There are three botanical species that figure into the symbolic representations in the Hebrew and early Christian scriptures, the grapevine, the olive tree, and the fig tree. Each of these is significant as a source of nourishment and economy in Israel, but even more importantly, participates in a symbolic complex that associates the nation of Israel with those plants, so that the plant becomes the symbol for Israel as a nation.
There are two important horticultural allegories in the Bible, the earlier of which is in Isaiah:
Isaiah 5:1-7
1 Now will I sing to my wellbeloved a song of my beloved touching his vineyard. My wellbeloved hath a vineyard in a very fruitful hill:
2 And he fenced it, and gathered out the stones thereof, and planted it with the choicest vine, and built a tower in the midst of it, and also made a winepress therein: and he looked that it should bring forth grapes, and it brought forth wild grapes.
3 And now, O inhabitants of Jerusalem, and men of Judah, judge, I pray you, betwixt me and my vineyard.
4 What could have been done more to my vineyard, that I have not done in it? wherefore, when I looked that it should bring forth grapes, brought it forth wild grapes?
5 And now go to; I will tell you what I will do to my vineyard: I will take away the hedge thereof, and it shall be eaten up; and break down the wall thereof, and it shall be trodden down:
6 And I will lay it waste: it shall not be pruned, nor digged; but there shall come up briers and thorns: I will also command the clouds that they rain no rain upon it.
7 For the vineyard of the LORD of hosts is the house of Israel, and the men of Judah his pleasant plant: and he looked for judgment, but behold oppression; for righteousness, but behold a cry.
We need not wonder whether or not the association between the vine and Israel is understood, as Isaiah makes it explicit. In this analogy, we have the vine, the vineyard, a master of the vineyard, a wild and natural fruit, and efforts of the master to improve the vine. Each of these elements show up in at least structural form in both the Zenos and Pauline olive tree allegories.
A significant difference in this analogy, however, is the final conclusion of the master of the vineyard. There comes a time when the master deems the vineyard unworthy of continued efforts. and so tears down the wall to destroy the vineyard. In Isaiah's writings there is an emphasis on the final Millennial events, and his analogy fits into that theme.
The most important horticultural allegory for establishing a context for Zenos allegory is found in Romans:
Romans 11:16-24
16 For if the firstfruit be holy, the lump is also holy: and if the root be holy, so are the branches.
17 And if some of the branches be broken off, and thou, being a wild olive tree, wert graffed in among them, and with them partakest of the root and fatness of the olive tree;
18 Boast not against the branches. But if thou boast, thou bearest not the root, but the root thee.
19 Thou wilt say then, The branches were broken off, that I might be graffed in.
20 Well; because of unbelief they were broken off, and thou standest by faith. Be not highminded, but fear:
21 For if God spared not the natural branches, take heed lest he also spare not thee.
22 Behold therefore the goodness and severity of God: on them which fell, severity; but toward thee, goodness, if thou continue in his goodness: otherwise thou also shalt be cut off.
23 And they also, if they abide not still in unbelief, shall be graffed in: for God is able to graff them in again.
24 For if thou wert cut out of the olive tree which is wild by nature, and wert graffed contrary to nature into a good olive tree: how much more shall these, which be the natural branches, be graffed into their own olive tree?
This allegory and that of Zenos (as cited by Jacob) are so clearly parallel that some type of connection if obvious. Understanding the possible connections between the two are essential from a polemical view, as one of the possibilities that must be explored is the modern copying of Paul's allegory into a modern Book of Mormon. If the Book of Mormon is true work (as we affirm it to be) then the allegory is ancient, and precedes Paul. Paul would be citing a known practice in the very least, and a known allegory in the most direct connection.
If, however the allegory of the olive tree were to be shown to originate with Paul, then the Book of Mormon usage would be greatly in question. Thus the understanding of Paul's allegory is an essential prelude to accepting and understanding the ancient allegory of Zenos in the Book of Mormon.
In Paul, the allegory has a very specific focus on the conceptual boundary between Jew and Gentile in the gospel. This single symbolic focus is much less complicated that Zenos' allegory which describes in symbolic fashion a larger number of events and peoples.
Paul's allegory depends upon three symbols, the root, and natural and wild branches. Where Isaiah's "wild fruit" was a symbol for evil works, Paul's use of the "wild" imagery is that of something foreign to the "natural" tree. The two uses differ in the symbolic sets they define. In Isaiah the natural/wild pair is used to stand for a conceptual pairing of good/evil. In Paul, however, the natural/wild pairing stands for Israel/Gentile, with no imprecation on the Gentile half of the pairing, indeed it will be the Gentile half that proves beneficial in the allegory. This essential difference in the nature of the allegories suggests that while horticultural allegories might be a acceptable mode of instruction Paul's allegory does not directly link to Isaiah as a source.
The removal of Isaiah as a source for Paul removes the clear antecedent that could have explained both Paul and Zenos (perhaps). The antiquity of the olive tree allegory prior to Paul depends upon the controversy over the accuracy of the practices described.
For a number of years, the standard interpretation of Paul has been rather unfavorable, such as this passage from the Interpreter's Bible commentary on Romans:
"At more than one point his ignorance of husbandry is disclosed: branches from a wild olive tree would not be grafted on a cultivated olive stock (if anything, the reverse would be done), and if they were, the grafted branches would not bear the fruit of the cultivated tree. (Acts Romans. The Interpreter's Bible.New York, Abingdon Press. 1954. 9:571)
This is an absolutely critical point, for it suggests that the essence of the Pauline allegory is based upon a misunderstanding of olive tree husbandry, and the entire allegory depends upon an error in reporting such practices. If that is the case, Zenos' earlier use of the same symbolism of grafting on wild branches would be suspect, as the longevity of an allegory with incorrect allusions would also be suspect, and the perpetuation of the error would point to a modern copying of Paul rather than an ancient practice with sufficient known understanding to ring true to the hearers of the allegory.
Baxter and Ziesler note the work of Sir William Ramsey in finding a virtual contemporary of Paul discussing the very idea of grafting wild branches onto an olive tree. That contemporary was named Columella:
"Columella writes a good deal about grafting, in De rustica 5.11.1-15 and De arboribus 26-27 (although a good deal of the material in the two works overlaps, even to the point of being straight repetition). He includes a considerable amount also about oleiculture, in De rustica from 5.9.16. He certainly thinks he knows what he is talking about, and it is interesting that in 5.9.16, almost in passing, he says that well-established trees that are failing to produce proper crops can be rejuvenated and made more productive if they are ingrafted with shoots from the wild olive". (Baxter, A.G., and J. A. Ziesler. "Paul and Arboriculture: Romans 11.17-24." In: Journal for the Study of the New Testament. 1985, 24:26).
Baxter and Ziesler conclude: "What Paul describes is therefore a perfectly possible process that would be undertaken to rejuvenate a tree." They further note a similar practice in modern Israel and in the Mediterranean. (Baxter, A.G., and J. A. Ziesler. "Paul and Arboriculture: Romans 11.17-24." In: Journal for the Study of the New Testament. 1985, 24:27.) Further confirmation comes from Hess, Fairbanks, Welch, and Driggs who also conclude that this is acceptable means of revitalizing the root of a tree (Hess, Wilford M., Daniel J. Fairbanks, John W. Welch, and Jonathan K. Driggs "Botanical Aspects of Olive Culture Relevant to Jacob 5" In: The Allegory of the Olive Tree." FARMS, Provo. p. 507).
With evidence that Paul is citing a legitimate practice, not only can we dismiss the suggestion that the Book of Mormon account must necessarily flow from Paul's allegory, but we may also suggest another solution to one of the reasons that Paul's allegory was questioned in the first place. It was noted by several modern commentators that Paul was a man of the city, and therefore would be unlikely to understand the intricacies of oleiculture (see, for instance,. Acts Romans. The Interpreter's Bible. New York, Abingdon Press. 1954. 9:571 and Baxter and Ziesler p. 25.)
While it is important to understand that there is a valid basis for the allegory, we must now answer the question of Paul's knowledge from a different perspective. His presumed ignorance of olive culture must be answered in reverse. If he did know of this rather unusual practice, how did such a citizen of the city know of the practice? Baxter and Ziesler simply restate Ramsay's assumption that the importance of olive culture created a de facto knowledge base of the means of caring for the trees (Baxter and Ziesler p. 26). While the importance of the olive is unquestioned, it is highly questionable that the importance of the products of the tree equate to a widespread understanding of the care of the tree, particularly argued against by the relative scarcity of ancient or modern writers understanding the legitimacy of the grafting in of wild branches, even though it was clearly attested anciently, and the olive culture has continued unabated into modern times.
The justification of Paul was sufficient response in and of itself, and the issue of the source of Paul's knowledge became a very secondary point. Into this space in the academic discussion, Zenos comes as an answer rather than as a copy. As a work that preceded Paul, and clearly understands the complexities of oleiculture, Zenos may have been either the ultimate source, or a parallel tapping of an oral source for a similar image. Paul would not, then, have been creating the allegory, but simply repeating an image that was known from alternate sources, sources that either trace to Zenos, or which preceded even Zenos as part of an oral understanding and imagery.