The good and eatable fish are separated by the fishers' skill from the bad and poisonous fish, so that the enjoyment of the good should not be spoilt by any of the bad getting into the "vessels" with them. The work of true sobriety is the same; from all pursuits and habits to choose that which is pure and improving, rejecting in every case that which does not seem likely to be useful, and letting it go back into the universal and secular life, called "the sea" (Matthew 13:47-48), in the imagery of the Parable.