Or, as we might more naturally put it, this plant is not growing well because it has not got enough fertiliser - that would be the causal use of 'because' that was discussed in the first section of this chapter. Note that in order to obtain the desired conclusion, it was necessary to include the word 'cause' (or the word 'because') in PI. If we had left PI as it is in the first version, then the inference to the conclusion in the second version would have been invalid. For it is certainly not true that if A is true (the plant hasn't enough fertiliser), and B is true (the plant isn't growing well), then A is the cause of B (though of course if A is the cause of B, then A and B are both true).
In fact this is not quite the whole argument, but only a sub-argument. In order to get the final conclusion, 'This plant is not growing well because we did not fertilise it', we'd have to add another premise after the given conclusion, 'If we had fertilised this plant, then it would have had enough fertiliser'.
Note that the correct reconstruction is not like this:
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