Chapter 16 of Rabbi Shloma Majeski’s Likkutei Mekoros, Volume 2, responds to the questions: Where does the Rebbe explain why he refers to the Pervious Rebbe when he actually means himself? Where does the Rebbe state that he and the Previous Rebbe are one and the same? (Underlined text is the compiler’s emphasis.)
12. As mentioned above (Section 2), the epithet “the two great luminaries” – referring to the Baal Shem Tov and the Alter Rebbe – indicates that the two great luminaries of Torah and Chassidus share a common purpose.
It is therefore understood that although their respective approaches appear to be opposites, they are not contradictory; they actually complement each other. (For this very reason, the birthdays of the Baal Shem Tov and the Alter Rebbe are the same day. Thus, celebrating their birthdays (for the purpose of strengthening going in their path, etc.) happens at once, in one farbrengen.)
In a deeper sense, the fact that the Baal Shem Tov and the Alter Rebbe complement and fulfill each other’s missions is not only that the Alter Rebbe in his generation complements or completes the purpose of the Baal Shem Tov, but also the reverse: the Baal Shem Tov [who lived prior to the Alter Rebbe] completes the Alter Rebbe.
With regard to physical, mundane experience, of course, the concept of providing completion only applies to the descendant, meaning that he completes the efforts of the predecessor.
But this is not so regarding spiritual matters, matters pertaining to the person’s eternal soul. To the soul, concerns of the predecessor are present in and influence even later generations, to the extent that it is possible to say that the one who is chronologically first completes the one who follows him (meaning that the spiritual influence of the first is perpetual).
How much more so in our case, when speaking about the soul of Nasi Doreinu, leader of our generation. A true Nasi is a faithful shepherd, who, even after his passing, “does not abandon the sheep of his flock” and “the deeds he has done” all the days of his life are ongoing. Also, his impact is not stagnant at the level it was at when he lived in this world; it continually increases and progresses.
(The latter concept finds explicit expression in Nigla (the non-mystical dimensions of Torah), “Just as his descendants are alive so is he alive” (Taanis 5b): “He is alive” (the ongoing life of the predecessor) is learned from the fact that “his descendants are alive.” It is therefore understood that just as the concept of the “life” of “his descendants” includes the concept of tzmicha, flourishing or developing – for their service in Torah study and the fulfillment of Mitzvos increases with added vitality and excitement – so too regarding “so is he alive” – the actions of the predecessor are perpetual and ever-increasing, etc)
It comes out that just as the Alter Rebbe, who lived two generations after the Baal Shem Tov, completed the purpose of the Baal Shem Tov in “spreading the wellsprings outward” (as above, Section 3), so too in reverse: the Baal Shem Tov completes the purpose of the Alter Rebbe (even in the generation of the Alter Rebbe) insofar as the leadership (and impact) of the Baal Shem Tov continues even in later generations.
Parenthetically, this does not contradict the general concept of “there is only one voice (i.e., authority) per generation; not two voices per generation,” as it follows the precedent of what is written elsewhere regarding the kingship of Shlomo in the time of Dovid. There is a seeming contradiction about their concurrent rule. It states in Tanach that Shlomo was coronated in the lifetime of Dovid (as Dovid HaMelech commanded). On the other hand, it is explicitly mentioned that after Dovid promised that Shlomo would reign on “this day,” they proclaimed, “Eternal life…to King Dovid” (See Melachim II 1:30-31 )
What emerges from this observation is that the reign of Shlomo in the time of Dovid was not actual kingship, per se (tantamount to having “two voices,” two sources of authority). Rather, Shlomo’s coronation was merely an expression of Dovid HaMelech’s sovereignty, for one of the powers of a king is that he may bestow his authority upon another. But the sovereignty of the viceroy is only an aspect and part of the king’s reign.
So too in our case, regarding “the two great luminaries.” Since the Alter Rebbe was the mameleh makom of the Baal Shem Tov, therefore, in the time of the Alter Rebbe, the leadership (and purpose) of the Baal Shem Tov was an aspect and part of the leadership of the Alter Rebbe. (It has been explained on several occasions that the very fact that the expression – “memalei makom– (literally, filling the place)” – is cited in Torah law proves that its meaning is to be understood in the simple, literal sense. Namely that the entire place (and significance/purpose) of the first person is “filled” by the “memalei makom,” (the one who assumes his role and position)
(From the address of 18 Elul 5745; Hisvaaduyos, pg. 2922-3)