Indeed the purely Materialist conception of Man cannot adequately account for selfless, sacrificial love, which argues for the existence of a transcendent source of love; a source that is outside nature.
1. Man experiences self-giving love.
2. The survival instinct required by Materialism cannot include self-giving love.
3. Self-giving love then must be transcendent to mere survival instinct.
4. Therefore, self-giving love must have a transcendent cause.
1. Peter Kreeft, Your Questions, God Answers, p.105, Ignatius Press (1994)