the metamorphosis of a caterpillar into a butterfly has been used to illustrate the conversion of an unregenerate person into a christian believer. the analogy is very thought-inspiring and moving. to imagine how an ugly and hideous caterpillar could become such a beautiful and lovely butterfly is simply astounding!
but upon closer examination, the metamorphosis of a caterpillar into a butterfly is not analogous to the conversion of an unregenerate person into a christian believer. it is not analogous on a very fundamental point — on the cause of the metamorphosis.
caterpillars change into butterflies because it is in the order of nature. in other words, all things being equal, all caterpillars change into butterflies at a certain point in their lives. a caterpillar matures into a butterfly, in its normal life cycle. nature urges the caterpillar to enter in its cocoon, awaiting the time it would spread its wings and become a beautiful and attractive fluttering being. a butterfly is simply a mature caterpillar.
on the contrary, unregenerate persons, in order of nature, do not change into christian believers at a certain point in their lives. an unregenerate person does not mature into a christian believer — never — he simply matures into an unregenerate man or woman, and dies unregenerate, in order of nature. all unregenerate persons do not mature into christian believers, in order of nature.
the change is caused by a supernatural act of God — God breathes new life into the unregenerate soul that is spiritually dead, to give him spiritual life. this is when his spiritual life begins. this is when he “spreads his wings and becomes a beautiful and attractive” spiritual being — not by order of nature, but by a sovereign and supernatural act of God.