Love Thy Neighbour as Thyself

LOVE THY NEIGHBOUR AS THYSELF (Lev. 19:18). R. Akiva says, "This is the great principle of the Torah." Ben Azzai says, "THIS IS THE BOOK OF THE GENERATIONS OF ADAM (Gen. 5:1), an even greater principle!"

-Sifra Weiss 88b.

R. Akiva hardly needs any introduction. Calling him one of the most significant figures of early Judaism is no exaggeration. More on him in later posts.
Simeon ben Azzai (or simply Ben Azzai) was a younger contemporary of Akiva's, and at one point betrothed to his daughter. Though he died young before he could be formally ordained as a rabbi, ben Azzai enjoyed long-lasting fame as a preacher and expounder of scripture.
In the midrash quoted above, r. Akiva defines the principle behind all of the Torah, or law, as loving one's neighbour. The laws contained in the Torah are meant to encourage love one for another. That is their raison de etre.
At first glance, Ben Azzai's scripture seems to have little relevance.
Why, indeed, how, is a book listing Adam's descendants a greater principle than loving one's neighbour as one's self?
for Ben Azzai, this verse refers to the Torah being about all of Adam's descendants. If one bears that in mind, the question won't arise, who is my neighbour? Ben Azzai does not contradict r. Akiva, but makes sure that there is no room for narrowly interpreting 'thy neighbour' as meaning only the house of Israel.