 Simply put, Ducasse defined some particular event c as the cause of some effect e if and only if c was the only change occurring in the immediate environment of e just prior to e. The striking of the match is the cause of the flaming match just insofar as the striking is the only change occurring in the immediate vicinity of the flaming match just prior to the flaming of the match. Ducasse intended this definition to rebut Hume’s claim that singular causal relations between particular events must be analyzed in terms of regularities between types of events (and thus laws). Indeed, Ducasse claimed that Hume was wrong to deny that we have the ability to perceive singular causal relations—this denial being the basis for Hume’s subsequent regularity account  (see 3.3).  For, according to Ducasse, we can perceive that some event is the only change in the immediate environment of some subsequent event just prior to that event’s occurrence. (We can, of course, be wrong in thinking that this is what we have in fact perceived. But as Ducasse points out, the same problem plagues Hume’s own account—we can be wrong that what we have perceived are instances of types which bear a regular relation to each other. But this does not lead Hume to hold that since we can’t infallibly perceive that some succession is an instance of a regularity, we cannot form the concept of causality in terms of regularity. The same thus applies to Ducasse’s own account.)