Board Thread:General Discussion/@comment-27136653-20180228205701/@comment-28517148-20180331125551

The fact is the Soul is the very essence of one's being that is kept inside their body - you need to pass through it to get to Soul. If magical attacks could harm the body then there would be no need for monsters to aim right into the Soul. Magical spears, lasers and others in some cases first come into contact with the body, but to make any harm they still need to hit the Soul. If the Soul manages to avoid those attacks, the body will stay unharmed (HP, the only indicator of taken damage, will not decrease). Otherwise, even if Frisk's Soul manages to avoid all lasers/spears, they still should take some kind of damage because it is mandatory for those lasers to make contact with the body in first place just to enter bullet board, but no such thing happened. Magical attacks cannot hurt the body. As for the Undyne's destroying physical objects, I would treat it as plot hole, neither first nor last in Undertale's story.