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The fact that we do survive is a product of the Imago Dei. We possess a mind that is capable of simple and complex thought- both of which can be and are used for survival. Unfortunately, man is fallen. One of the results of this fallen nature is the fact that man is self-focused (prideful and narcissistic). This causes man to focus acutely on his survival (survival is not wrong in itself, but the desire for it causes many to make choices based on a certain level of paranoia). Man will use this mind to come up with "ways of survival" that violate the intrinsic, equal value of other human beings (typically the illogical conclusion is one that violates another human life. They "reason" that it is the only option when it really is not). Murder is an example. In Christianity, murder is a sin because it is a direct insult to God, Himself ("I think so little of God and so highly of myself, that I will destroy a reflection of His value and His nature to further my own existence.").