4 ideas
Friendship cannot form across a wide gap in fortune — the well-fed and the destitute cannot be true friends because unequal circumstances corrupt the mutual give-and-take. Shared vulnerability and comparable stakes are preconditions for trust, not incidental to it.
Cooperation and mutual aid, not competition, are the primary drivers of species survival and social organization — animals and humans build survival networks by supporting each other. Solidarity is treated as a biological and evolutionary force rather than a moral luxury.
A friendship is strengthened, not weakened, when one party privately believes he is the superior of the two. The felt hierarchy resolves competition into stable patronage, letting the 'superior' feel generous and the other feel valued.
Distinguishing true friends from false ones works like vetting a job applicant: you test their reliability under conditions of cost, not comfort. Declarations of loyalty are cheap; only behavior when the friendship demands sacrifice reveals whether the bond is genuine.