Many natural patterns, such as the arrangement of buds on a stem, accord with the series of Fibonacci numbers, and Fibonacci spirals are also observe… - Mary Midgley

Speaking of an institution such as marriage as natural is, of course, paying it a compliment, the compliment of saying that it meets a fairly central human need. The fact that it is found in some form in every human society is in a way enough to show. But it might be thought that marriage became thus widespread only because it was, like adequate sanitation, a means to an end. This is pretty certainly what Hume thought, as evidenced by his very confused contrast of natural with artificial virtues. He regarded human sagacity simply as the power to calculate consequences, and counted chastity and fidelity, with justice, as artificial virtues, devices designed merely to produce safety and promote utility. In a species as emotionally interdependent as man this view of marriage is nonsense. Pair-formation could never have entered anybody's head as a device deliberately designated to promote utility.

The contrary, literalist campaign within Christianity is actually quite recent. It developed among more or less extreme Protestants after the Reformation – largely indeed in the last century in the US. It was consciously designed as a competitor with science, providing equal certainty by comparable methods. It is thus a political phenomenon, acting in some ways like a cargo cult. It has enabled relatively poor and powerless people to use their Bibles (which the Protestant Reformers had provided) to shape a rival myth of their own. They see this as an alternative to the materialist glorification of science and technology which they have perceived – with some reason – as the oppressive creed of those in power.

The symbolism of meat-eating is never neutral. To himself, the meat-eater seems to be eating life. To the vegetarian, he seems to be eating death. There is a kind of gestalt-shift between the two positions which makes it hard to change, and hard to raise questions on the matter at all without becoming embattled.