Another good example of how theology gets read back into texts where it doesn’t belong is provided by the argument that the gospel first appears in Genesis 3:15. The singular “seed” of the woman, who will crush the head of the serpent, is taken to be a prophecy of the coming messiah. It’s known as the “protevangelium”. The argument cannot be defended exegetically as we shall see—and as even Calvin reluctantly admitted:
…other interpreters take the seed for Christ, without controversy; as if it were said, that some one would arise from the seed of the woman who should wound the serpent’s head. Gladly would I give my suffrage in support of their opinion, but that I regard the word seed as too violently distorted by them; for who will concede that a collective noun is to be understood of one man only? Further, as the perpetuity of the contest is noted, so victory is promised to the human race through a continual succession of ages. I explain, therefore, the seed to mean the posterity of the woman generally. (Commentary on Genesis)
But the point I will emphasize is that it illustrates the pervasive failure of dogmatic theologies to respect the integrity and boundaries of the text.