_{Source: p 48 Bottom - 49 Top. Causation: A Very Short Introduction (1 ed 2013) by Stephen Mumford, Rani Lill Anjum.}

###The Production Process The argument from additive interference has a broad significance.
[1.] Even in those cases where a cause successfully produced its effect, it did not do so by necessitating it.
[2.] There are some actual cases of failure of causation, due to additive interference [hereafter AIF];
but even in the cases where there was no such interference, there could have been. No cause necessitates its effect, therefore, if the effect could have been prevented by an additional factor.

What this suggests is that, even for anti-Humeans, a distinction should be made between the notions of causal production and causal necessitation. Hume attacked necessity in causation and left in its place only pure contingency. If one thinks something is inadequate about his constant conjunction account, it doesn’t follow automatically that one has to defend necessary connections in nature, as opposed to them residing only in ‘relations of ideas’.

Per the first paragraph, I do not understand how causation can be fairly asserted to fail because of some AIF, because the existence of AIF changes the facts.

3. Per my numbering, 1 differs from 2, because only 2 contains the AIF. So causation applies to different facts in 1 and 2. So I would conclude that causation succeeds in 1, but fails in 2. In contrast, the book appears to consider causation applied equally across 1 and 2.

_{Source: p 48 Bottom - 49 Top. Causation: A Very Short Introduction (1 ed 2013) by Stephen Mumford, Rani Lill Anjum.}

###The Production Process The argument from additive interference has a broad significance.
[1.] Even in those cases where a cause successfully produced its effect, it did not do so by necessitating it.
[2.] There are some actual cases of failure of causation, due to additive interference [hereafter AIF];
but even in the cases where there was no such interference, there could have been. No cause necessitates its effect, therefore, if the effect could have been prevented by an additional factor.

What this suggests is that, even for anti-Humeans, a distinction should be made between the notions of causal production and causal necessitation. Hume attacked necessity in causation and left in its place only pure contingency. If one thinks something is inadequate about his constant conjunction account, it doesn’t follow automatically that one has to defend necessary connections in nature, as opposed to them residing only in ‘relations of ideas’.

I do not understand how causation can be fairly asserted to fail (in the 1st paragraph) because of some AIF, because AIF adds to, and so changes, the given previous state.

3. Per my numbering, 1 differs from 2, because only 2 contains the AIF. So causation applies to different facts in 1 and 2. So I would conclude that causation succeeds in 1, but fails in 2. In contrast, the book appears to consider causation applied equally across 1 and 2.