Auden begins by describing a mood reading of many during that time period.  He states that  "waves of anger and fear circulate...the unmentionable odour of death offends the September night" (ll.6, 10-11O).  He then hypothesizes that the reason behind all of the recent evils (World Wars) that have occurred is "those to whom evil is done do evil in return"(l.22-23).  He says that many have pondered over the nature of evil, philosophized it into nullification, and with no point because "we must suffer them all again"(l.34).  He then turns the cause inward, to individuals, saying that we all crave "to be loved alone." (l.67).  In the last stanza, he says that we all have a voice and seek a connection with one another, that "dotted everywhere,  ironic points of light flash out wherever the Just exchange their messages".

All of this leads to one main thesis:  Evil exists, it will always exist, but one way to survive it is to use our voices to love one another, to connect, and to speak the truth, despite it all.