Pirkei Avot 1:6

"Yehoshua ben (son of) Perachia and Nittai of Arbel received the transmission from them [the rabbis of Mishna 4]. Yehoshua ben Perachia said: Make for yourself a rabbi, acquire for yourself a friend, and judge every person favorably."

The underlying subject of this mishna is how to live.  What do making for yourself a rabbi, acquiring for yourself a friend and judging every person favorably have in common?  It is making right choices in everyday life.  A rabbi knows the law and the priorities among the mitzvot, and how they apply practically to everyday life, and a rabbi that we make for ourself will come to know us as well.  A friend can know us, and our strengths and weaknesses, and help us make decisions and sort out our priorities by helping us see ourselves and our choices from another perspective.  Judging others favorably acknowledges the difficulty of applying the mitzvot to the myriad of daily choices we are faced with, and the possibility that the other person may be trying to do so.

There are four premises implicit in this mishna:  first, that we are ethical beings, who ought to, and want to act ethically or in accordance with halacha; second, that it is not always obvious how to do so; living ethically or halachically requires knowledge and thoughtfulness; and third, that living ethically or halachically requires the assistance of others, who know the law, and who know us; and fourth, that others may be trying to live ethically or halachically as well.

There are further implications from these premises.  First, that anyone, Jew or gentile, can choose to live ethically or not.  The art of living ethically is difficult, and requires assistance of others, but is clearly meritorious.  Second, that ethical living for a Jew is defined by reference to Torah, which is why we are advised to take a rabbi for ourselves.  Third, that we act ethically or halachically by looking for the best in others.  What this means is to love others, for love is essentially favorable interpretation of the loved one.  Loving others inclines us to act ethically or halachically toward them.  Love is the meta-mitzvah in our relationships with other people, because it inclines us to perform other miztvot toward others.  Of course, halacha also contains mitzvot in our relationship to God, but God in his infinite wisdom commands us to treat others with love.