A further issue is whether the size or degree of an individual’s causal contribution to a threat affects their liability. An affirmative answer seems quite intuitive. For example, several writers argue that civilian contributions to unjust wars are too causally insignificant to generate liability (or at least liability to defensive killing) (Fabre 2009a: 60–61; McMahan 2009: 225) More precisely, the idea here is that (i) individuals can causally contribute to threats to a greater or lesser degree, and (ii) that the harm to which an individual is liable is sensitive to the degree of contribution.