Carnal is viewing all things from a this world perspective. Christ said we live in the spirit. Christians should be spiritually minded as Paul said rather than carnally minded meaning we view things from a spiritual perspective rather then a physical this world perspective.
It can also be expressed as, “This world is not my home.”
The unsaved world acts as if this world ought to be their home, and at best they are helped to do so by religion. Anyone who thinks otherwise is dismissed as kooky.