Rabbi Mordechai Willig
Moshe spoke to Hashem saying, "May Hashem appoint a man over the assembly who shall go out before them" (27:15-17). Rashi explains that as soon as Moshe was told that he would die and not enter Eretz Yisroel (27:13) he put aside his own concerns and dealt with those of the public. Yet, according to a later Rashi (27:16), Moshe said, "The time has come for me to request my concerns, that my son should inherit my greatness," which would seem to contradict Rashi's earlier statement.
Hashem said to Moshe, "Take Yehoshua and place your hand on him" (27:18). Didn't Moshe realize that Yehoshua was worthier than his own sons were? The answer to this question is based on yet another statement of Rashi (Devarim 31:7). Moshe called Yehoshua and said to him, "Be strong because you shall come with the people to the land" etc. Moshe said, "The elders of the generation shall be with you. Everything should be done according to their opinion and advice." But Hashem said (31:23) "Because you shall bring B'nai Yisroel to the land etc...Even against their will. Everything depends on you. Take a rod and hit their head. There is one leader for a generation, not two."
The two formulations, apparently contradictory, are, in fact, complementary. Moshe served as the head of the Sanhedrin (Sanhedrin 2a), as well as the king of Israel (Ibn Ezra 33:5). Yehoshua assumed both of these positions. As the head of the Sanhedrin, Moshe considered the opinion of the elders, and told Yehoshua to do the same. Hashem's formulation referred to Yehoshua's role as the king, which would require forceful and exclusive leadership.
Moshe requested that his son succeed him as the king. Indeed, if a son is suitable for leadership, he succeeds his father (Rashi 17:20), even if others are more worthy. The reason for filial succession is the avoidance of machlokes, which is nearly inevitable if everyone is a candidate. When Moshe requested "his concerns", it was really "the concerns of the public", to prevent a battle over the succession.
Hashem responded that he wanted to have one leader to serve as the king and the head of the Sanhedrin. Yehoshua was the only one who could assume both positions.
Hashem told Moshe to place one hand on Yeshoshua, but he placed both hands on Yehoshua, and filled him with wisdom (Rashi, Bamidbar 27:23). Apparently, Moshe realized all along that Yehoshua would lead the Sanhedrin. His dialogue with Hashem related only to the kingship. Hashem told Moshe to appoint Yehoshua as the king, who would lead the people in battle (Rashi 17). This appointment required that Moshe place one hand on Yehoshua. However, Moshe appointed Yehoshua in both capacities, placing both hands on him and filling him with the wisdom of Torah as well as the strength for battle.
Moshe requested a bifurcated leadership because he knew that this was the usual way. Indeed, of the forty Torah leaders (listed by the Rambam in his introduction to Mishne Torah) from Moshe until Rav Ashi edited the Talmud, only very few were kings as well (Moshe, Yehoshua, and Dovid).
Hashem responded "This is not what has entered into My mind (alsa b'machshava)" The expression "alsa b'machshava" refers to an ideal state which can not be sustained practically (see Rashi Breishis 1:1). Moshe was ready to abandon the ideal of one leader, a system that lessens the constant conflict between religious and temporal authority, as impractical. But Hashem insisted that it be maintained for one more generation in the person of Yehoshua.
In our time and place, there is no national authority, religious or temporal, in the Jewish community. Religious authority is rejected or marginalized even by parts of religious society. Scholarship and leadership are viewed by some as mutually exclusive.
Even when practicality leads to a separation of power, or influence, it is important to recognize that this is not an ideal. Moshe, Yehoshua, and Dovid were ideal national religious leaders who led politically and militarily as well. This is impossible for many reasons nowadays.
Yet great Torah scholars led local and larger communities, narrowly defined, throughout Jewish history. The Rav's celebrated eulogy for Rav Chaim Ozer, the gadoal hador who was consulted on worldly matters as well, describes but one example. All enduring, successful movements in religious Torah society have been led by Torah scholars. Of course, such leaders must realize that many decisions are beyond their purview, and must have love and respect for the laity and its proper leaders. The lessons learned from Moshe and Yehoshua must inform Torah society's understanding of leadership for all generations