It strikes me that Karma and the belief in heaven and hell are equivalent in their socio-psychological-moral function. They both serve to affirm that the universe is ultimately just and that moral action is worthwhile because it 'really counts'. In addition, they serve to explain that the societies we live in are just.
I don't see any evidence that either of the explanations are true. They may be comforting but in my experience, a lot of ammoral people live satisfying lives and good people suffer. Both systems depend on existence either before or after this life. I don't see any reason to think there's any existence beyond this one.

Can we live in an unjust universe?

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13