In God’s original design, human sexual conduct was to occur within the context of marriage between one man and one woman. The first chapter of the Bible says, “God created man in his own image, in the image of God he created him; male and female he created them” (Genesis 1:27). Differentiation of the human race into two complementary sexes (“male and female”) is the first fact mentioned in connection with being “in the image of God.” In Genesis 2, which describes in more detail the process summarized in 1:27, God said, “It is not good that the man should be alone; I will make him a helper fit for him” (Genesis 2:18). Genesis then applies the example of Adam and Eve to all marriages: “Therefore a man shall leave his father and his mother and hold fast to his wife, and they shall become one flesh” (Genesis 2:24). This “one flesh” sexual union was thus established as the pattern for marriage generally,...