A read in context lets us know the brothers (and sisters) not in darkness are not all the peoples of the earth, but only those who have been delivered from darkness to Light.
And then we read: But since.
Isn’t that great?!
Since we have been delivered to the Light, we can be sober, we can put on the breastplate of faith and love with the hope of our salvation, and walk in the Light amid great darkness around us. 

But since we have this Light, let us be mindful of those around us still walking in darkness, and present ourselves daily to JESUS, asking Him to make us useful to Him for them.

Holy hugs, my Friends, Kathie