http://revach.net/article.php?id=4264

Section:  Avodah   Category: Pirkei Avos
Pirkei Avos: Rav Nosson Gestetner - Achdus Is Often An Optical Illusion
The Mishna (4:11) says that, "Kol Kneisia SheHi L'Shem Shamayim Sofa L'Hiskayem, V'SheEina LShem Shamayim Ein Sofa L'Hiskayem".  Any gathering that is L'Shem Shamayim will stand at the end, but any gathering that is not will not stand at the end.  There are two questions here.  First, if there is Achdus shouldn't the gathering succeed?  Second why Sofa L'hiskayem, why only at the end?

MiShel HaAvos brings from Rav Nosson Gestetner a Mashal.  Two people are traveling to the same destination and there are two roads that go there.  Even if they each choose to travel on a different road at the end they will meet in the same place.  However two travelers that are traveling together but to different destinations, although they are now in unity, eventually they will split up and end up in different places.

You can have a gathering with heated debate and many people proposing vastly different approaches to solve a problem.  While there seems to be little achdus, if each person is arguing L'Shem Shamayim they all ultimately will arrive at the same place.  They will achieve Kavod Hashem and Sofa L'Hiskayem.   However if it is not L'Shem Shamayim then even if everyone agrees in very polite fashion on the same course of action, they will eventually end up in far different places, Ein Sofa L'Hiskayem.  Why? Because each one is acting for a different cause, themselves!