Suppose it has been fully established that event x causes event y, in circumstance a. Would it be possible to correctly deduce that event x is occuring purely by observing that event y is occuring in circumstance a? Or can the same effect (in the same conditions) have multiple causes?
There is a logical fallacy which captures the trouble here, called Affirming the Consequent.
Informally, it is the pattern of arguing anything like: "(1) If it is raining, then the ground will be wet. (2) The ground is wet. (3) Therefore, it is raining." This is invalid because there might be other causes of the ground being wet -- like someone spraying water on it from a hose.
More formally, it is the pattern of arguing:
You hinted at the way through this, though: what must be established in your example isn't just that x causes y, but that only x causes y. Here is a valid logical pattern that would reflect that idea:
Whether you can establish that y has exactly one cause depends on y: some things do, some things don't.
answered Feb 03 '11 at 16:14
Greg Perkins ♦♦