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1Thess 5:13b . . Live in peace with each other.
In this instance, "each other" probably refers to fellow believers.
The category of peace Paul is talking about is social; viz: harmony in personal relations. The Hippies and the peace-nics failed to achieve peace primarily because they couldn't be civil among themselves unless they were high on mood-altering drugs.
Peace can be defined as: calm, pacific, tranquil, at rest, quiet, and free of trouble and strife.
A lack of peace is characterized by war, quarrelling, debating, vendettas, hostility, grudging, fault finding, nit picking, chafing, competition, rivalry, cold shouldering, factions, taking sides, cliques, hostility, militancy, disorder, antagonism, fighting, conflict, struggles, et al.
NOTE: Never assume that everyone you meet in church is a fellow believer. Going to church on Sunday is just what some people do, and probably have done ever since they were kids. There was a time when going to church on Sunday was considered good citizenship; and quite a few people were there for no other reason; i.e. church sort of fills out their social résumé. And then some people attend church because they're lonely and wanting to meet some new friends; etc, etc, etc, etc.
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