Free The Science of Discworld Revised Edition by Terry Pratchett Page A

For instance, most people seem to accept that in general terms women should be permitted abortions during the earliest stages of pregnancy but not during the very late stages. ‘Where you draw the line’, though, is hotly debated – and of course some people wish to draw it at one extreme or the other. There are similar debates about exactly when a developing embryo becomes a person, with legal and moral rights. Is it at conception? When the brain first forms? At birth? Or was it always a
potential
person, even when it ‘existed’ as one egg and one sperm?
    The ‘draw a line’ philosophy offers a substantial political advantage to people with hidden agendas. The method for getting what you want is first to draw the line somewhere that nobody would object to, and then gradually move it to where you really want it, arguing continuity all the way. For example, having agreed that killing a child is murder, the line labelled ‘murder’ is then slid back to the instant of conception; having agreed that people should be allowed to read whichever newspaper they like, you end up supporting the right to put the recipe for nerve gas on the Internet.
    If we were less obsessed with labels and discontinuity, it would be much easier to recognize that the problem here is not where to draw the line: it is that the image of drawing a line is inappropriate. There is no sharp line, only shades of grey that merge unnoticed into one another – despite which, one end is manifestly white and the other is equally clearly black. An embryo is not a person, but as it develops it gradually becomes one. There is no magic moment at which it switches from non-person to person – instead, it merges continuously from one into the other. Unfortunately our legal system operates in rigid black-and-white terms – legal or illegal, no shades of grey – and this causes a mismatch, reinforced by our use of words as labels. A kind of triage might be better:
this
end of the spectrum is legal,
that
end of the spectrum is illegal, and in between is a grey area which we do our best to avoid if we possibly can. If we can’t avoid it, we can at least adjust the degree of criminality and the appropriate penalty according to whereabouts in the spectrum the activity seems to lie.
    Even such obviously black-and-white distinctions as alive/dead or male/female turn out, on close examination, to be more like a continuous merging than a sharp discontinuity. Pork sausages from the butcher’s contain many live pig cells. With today’s techniques you might even clone an adult pig from one. A person’s brain can have ceased to function but their body, with medical assistance, can keep going. There are at least a dozen different combinations of sex chromosomes in humans, of which only XX represents the traditional female and XY the traditional male.
    Although the Big Bang is a scientific story about a beginning, it also raises important questions about becomings. The Big Bang theory is a beautiful bit of science – very nearly consistent with the picture we now have of the atomic and the subatomic world, with its diverse kinds of atom, their protons and neutrons, their clouds of electrons, and the more exotic particles that we see when cosmic rays hit our atmosphere or when we insult the more familiar particles by slamming them together very hard.
    Physicists have now found, or perhaps invented, the allegedly ‘ultimate’ constituents of these familiar particles (more exotic things known as quarks, gluons … at least the names are becoming familiar).
    The Holy Grail of particle physics has been to find the ‘Higgs boson’, which – if it exists – explains why the other particles have mass. In the 1960s Peter Higgs suggested that space is filled with a kind of quantum treacle called the Higgs field. He suggested that this field would exert a force on particles through the medium of the Higgs boson, and that force would be observed as mass. For 30 years,