Because symbols and metaphors are not exact sciences, and in some cases could mean any number of things. For instance, some people will see a snake and forever think of it’s image in the Bible as a symbol of Satan, or any manner of dastardly things such as, “death, destruction, evil, a penetrating legless essence, and/or poison.” But other people may not necessarily make that connection, but instead looks at the snake in a different way; “when intertwined with the tree of life (Christian) it represents good, and it can also be associated with healing and/or rebirth; as it sheds its skin.”
If one person interprets that snake as “evil”, and another interprets is as “good”, who is right?
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