 Slippery slope arguments come in various versions. One (but not the only) way of classifying them has been to refer to logical, psychological and arbitrary line versions. The common feature of the different forms is the contention that once the first step is taken on a slippery slope the subsequent steps follow inexorably, whether for logical reasons, psychological reasons, or to avoid arbitrariness in ‘drawing a line’ between a person’s actions. (For further discussion see, e.g., Rachels 1986; Brock 1992; Walton 1992.)