 Woollard returns to Foot’s (1978, 1984, 1985) sequence account. However, she argues that Foot’s account is incomplete because it does not tell us how to distinguish enabling from sustaining, why enabling is grouped with forbearing to prevent, or what sustaining and initiating have in common. On Woollard’s view, the key question is whether the relevant fact about the agent’s behavior is part of the sequence leading to harm. Woollard distinguishes between substantial and non-substantial facts. Substantial facts are by nature suitable to be part of a sequence. Non-substantial facts normally count as mere conditions for a sequence. Thus anything that is relevant to a sequence through a non-substantial fact will normally be a mere condition rather than part of the sequence. However, non-substantial facts can count as relatively substantial and part of a sequence under special circumstances, if for example, they are facts about the absence of a barrier that belongs to the victim.