Clarification: Since Har Gerizim and Har Eival were situated sixty Mil away from the Yarden, as we learned in Perek Eilu Ne'emarin.

Question: But surely, he did the correct thing, seeing as the Pasuk in Ki Savo specifically obligates setting up the stones on Har Eival? And what could he (Yehoshua) have done if he did find Har Gerizim and Har Eival until he reached them?

Introduction to Answer (Part 1): The Gemara in Perek Ein Ne'emarim cites a Machlokes Tana'im, where R. Yehudah, commenting on the Pesukim 1. "ha'Lo Heimah be'Eiver ha'Yarden" and 2. "ha'Yoshev ba'Aravah", explains 1. 'me'Eiver la'Yarden va'Eilech' - by which he means 'far from the Yarden', and b. that this refers to Har Gerizim and Har Eival', where the Kutim currently live.

Answer (Part 2): Whereas R. Eliezer says " ha'Lo Heimah be'Eiver ha'Yarden" - 'close to the Yarden'. It cannot mean far from the Yarden, since the Pasuk (Ibid.) writes "And it shall be, when you cross the Yarden. R. Eliezer clearly holds that the Pasuk is referring to the Har Gerizim and Har Eival that are close to the River Yarden, and that there are two sets of mountains bearing the same names.

Introduction to Answer (Part 3): The Yerushalmi, on the other hand, asks how R. Eliezer establishes "Har Gerizim" and "Har Eival" (seeing as they were situated sixty Mil away from the Yarden). And it answers that they made two mounds of earth, one of which they named 'Har Gerizim', and the other, 'Har Eival'; and it concludes that, according to R. Yehudah they travelled sixty Mil that day, whereas according to R. Eliezer, they did not move from their place.

Answer (Part 1): So it transpires that R. Shilo in our Sugya interprets the Pesukim like R. Eliezer, in which case, Yehoshua ought to have done what R. Eliezer said, but he went to the Har Gerizim and the Har Eival that were in the vicinity of the Kutim.

Answer (Part 2): Whereas according to Rav, who holds that Yehoshua acted correctly, could hold either like R. Yehudah or like R. Eliezer.

Clarification: This is speaking specifically in the fields and on the mountains, where one does not generally find people, for that is where demons are commonly found, even during the day, like we learned in the last Perek of Yevamos, in the case where someone ascended the mountain. But in the city, even at nighttime we are not afraid (that it might be a demon), because otherwise, how is one permitted to greet ", and how is a woman able to receive a Get, at nighttime?

Implied Question: Why does the Gemara not answer here that he saw the 'shadow of the shadow'?

Answer: Because a shadow is not discernable at night-time.