We can form some image of the good that goodwill does and the truth that faith discloses if we think in terms of the warmth and light of the sun. When the light that radiates from the sun is united to warmth, as is the case in spring- and summertime, then everything on earth sprouts and blossoms. When there is no warmth in the light, though, as is the case in wintertime, then everything on earth becomes dormant and dies. Spiritual light is the truth that faith discloses, and spiritual warmth is love.
This enables us to form an image of what people of the church are like when faith is united to goodwill in them. They are just like a garden or park. Their image when faith is not united to goodwill in them is like that of a wasteland and a land buried in snow.
The assurance or trust that is ascribed to faith and is referred to as “truly saving faith” is not a spiritual assurance or trust but an earthly one, if it is a matter of faith alone. Spiritual assurance or trust derives its essence and life from the good that love does but not from the truth that faith discloses apart from that good. The assurance that belongs to faith separated from good is dead, so real assurance is not possible for us when we are leading evil lives. An assurance that we are saved, no matter how we have lived, because of the Lord’s merit with the Father does not come from truth either.
from Regeneration, Page 18