 Some authors respond to this argument by rejecting premise 1, positing a symmetric notion of causal dependence, which for non-simultaneous cause-effect pairs is also time-symmetric (Ney 2009). A potential problem for this response is that it appears to collapse the distinction between the notions of dependence and causation and may have difficulties explaining how a symmetric notion of causal dependence (as opposed to an asymmetric notion of causation) can play a role in elucidating the apparently asymmetric notions of intervention, responsibility, or explanation. These problems appear especially pressing from the perspective of the functional project. Thus, Ney’s proposal is most promisingly considered as part of a metaphysical project of uncovering the metaphysical grounds of causal claims.